From 979177744f806899d187ea15513d6b02d5193291 Mon Sep 17 00:00:00 2001
From: Mateusz Samsel <m.samsel@cksource.com>
Date: Tue, 12 Dec 2017 14:49:14 +0100
Subject: [PATCH 01/27] Some working solution for using XHR with filebrowser.

---
 plugins/dialogui/plugin.js    |  1 +
 plugins/filebrowser/plugin.js | 42 ++++++++++++++++++++++++++---------
 plugins/filetools/plugin.js   |  9 +++++++-
 3 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/plugins/dialogui/plugin.js b/plugins/dialogui/plugin.js
index 04a9ee3431e..1e4e0114844 100644
--- a/plugins/dialogui/plugin.js
+++ b/plugins/dialogui/plugin.js
@@ -743,6 +743,7 @@ CKEDITOR.plugins.add( 'dialogui', {
 				myDefinition.className = ( myDefinition.className ? myDefinition.className + ' ' : '' ) + 'cke_dialog_ui_button';
 				myDefinition.onClick = function( evt ) {
 					var target = elementDefinition[ 'for' ]; // [ pageId, elementId ]
+					// onClick.call() will create XHR request (if possible) and prevent of using submit method.
 					if ( !onClick || onClick.call( this, evt ) !== false ) {
 						dialog.getContentElement( target[ 0 ], target[ 1 ] ).submit();
 						this.disable();
diff --git a/plugins/filebrowser/plugin.js b/plugins/filebrowser/plugin.js
index 5b9c3b67e1a..bc205d4cf91 100644
--- a/plugins/filebrowser/plugin.js
+++ b/plugins/filebrowser/plugin.js
@@ -114,6 +114,7 @@
  */
 
 ( function() {
+	'use strict';
 	// Default input element name for CSRF protection token.
 	var TOKEN_INPUT_NAME = 'ckCsrfToken';
 
@@ -200,7 +201,7 @@
 		}
 	}
 
-	// The onlick function assigned to the 'Upload' button. Makes the final
+	// The onclick function assigned to the 'Upload' button. Makes the final
 	// decision whether form is really submitted and updates target field when
 	// file is uploaded.
 	//
@@ -297,22 +298,41 @@
 				if ( url ) {
 					var onClick = element.onClick;
 					element.onClick = function( evt ) {
-						// "element" here means the definition object, so we need to find the correct
-						// button to scope the event call
 						var sender = evt.sender;
-						if ( onClick && onClick.call( sender, evt ) === false )
+						var fileInput = sender.getDialog().getContentElement( this[ 'for' ][ 0 ], this[ 'for' ][ 1 ] ).getInputElement();
+						// Backward compatibility for IE8 and IE9 (https://cksource.tpondemand.com/entity/3117).
+						if ( editor.config.filebrowser_forceSubmit || !( CKEDITOR.plugins.clipboard && CKEDITOR.plugins.clipboard.isFileApiSupported ) ) {
+							// "element" here means the definition object, so we need to find the correct
+							// button to scope the event call
+							if ( onClick && onClick.call( sender, evt ) === false ) {
+								return false;
+							}
+
+							if ( uploadFile.call( sender, evt ) ) {
+								// Append token preventing CSRF attacks.
+								appendToken( fileInput );
+								return true;
+							}
+
 							return false;
+						} else {
+							if ( uploadFile.call( sender, evt ) ) {
+								var loader = editor.uploadRepository.create( fileInput.$.files[ 0 ] );
+								// loader.loadAndUpload( sender.getDialog().getContentElement( this[ 'for' ][ 0 ], this[ 'for' ][ 1 ] ).action );
 
-						if ( uploadFile.call( sender, evt ) ) {
-							var fileInput = sender.getDialog().getContentElement( this[ 'for' ][ 0 ], this[ 'for' ][ 1 ] ).getInputElement();
+								loader.on( 'uploaded', function( evt ) {
+									var response = evt.sender.responseData;
 
-							// Append token preventing CSRF attacks.
-							appendToken( fileInput );
-							return true;
-						}
+									setUrl.call( evt.sender.editor, response.url, response.message );
+
+								} );
 
+								loader.loadAndUpload( CKEDITOR.fileTools.getUploadUrl( editor.config, 'image' ) );
+								// Return false to not trigger submit option in dialogui.
 
-						return false;
+							}
+							return false;
+						}
 					};
 
 					element.filebrowser.url = url;
diff --git a/plugins/filetools/plugin.js b/plugins/filetools/plugin.js
index f1ca0f2f9fd..953262da248 100644
--- a/plugins/filetools/plugin.js
+++ b/plugins/filetools/plugin.js
@@ -48,7 +48,8 @@
 			editor.on( 'fileUploadRequest', function( evt ) {
 				var fileLoader = evt.data.fileLoader,
 					$formData = new FormData(),
-					requestData = evt.data.requestData;
+					requestData = evt.data.requestData,
+					header;
 
 				for ( var name in requestData ) {
 					var value = requestData[ name ];
@@ -64,6 +65,12 @@
 				// Append token preventing CSRF attacks.
 				$formData.append( 'ckCsrfToken', CKEDITOR.tools.getCsrfToken() );
 
+				if ( editor.config.xmlHttpRequestHeaders ) {
+					for ( header in editor.config.xmlHttpRequestHeaders ) {
+						fileLoader.xhr.setRequestHeader( header, editor.config.xmlHttpRequestHeaders[ header ] );
+					}
+				}
+
 				fileLoader.xhr.send( $formData );
 			}, null, null, 999 );
 

From 7bf2375f860bd638064983ede4e432d8dcd79c2c Mon Sep 17 00:00:00 2001
From: Mateusz Samsel <m.samsel@cksource.com>
Date: Wed, 13 Dec 2017 13:24:42 +0100
Subject: [PATCH 02/27] Few improvements to using XHR with uploading images.

---
 plugins/dialogui/plugin.js    | 12 +++++++++---
 plugins/filebrowser/plugin.js | 33 +++++++++++++++------------------
 2 files changed, 24 insertions(+), 21 deletions(-)

diff --git a/plugins/dialogui/plugin.js b/plugins/dialogui/plugin.js
index 1e4e0114844..fdf08c7cff8 100644
--- a/plugins/dialogui/plugin.js
+++ b/plugins/dialogui/plugin.js
@@ -743,9 +743,15 @@ CKEDITOR.plugins.add( 'dialogui', {
 				myDefinition.className = ( myDefinition.className ? myDefinition.className + ' ' : '' ) + 'cke_dialog_ui_button';
 				myDefinition.onClick = function( evt ) {
 					var target = elementDefinition[ 'for' ]; // [ pageId, elementId ]
-					// onClick.call() will create XHR request (if possible) and prevent of using submit method.
-					if ( !onClick || onClick.call( this, evt ) !== false ) {
-						dialog.getContentElement( target[ 0 ], target[ 1 ] ).submit();
+
+					// If exists onClick in elementDefinition, then it is called and checked response type.
+					// If it's posiblle, then XHR is used, what prevents of using submit.
+					var responseType = onClick && onClick.call( this, evt );
+
+					if ( !onClick || responseType !== false ) {
+						if ( responseType === 'form' ) {
+							dialog.getContentElement( target[ 0 ], target[ 1 ] ).submit();
+						}
 						this.disable();
 					}
 				};
diff --git a/plugins/filebrowser/plugin.js b/plugins/filebrowser/plugin.js
index bc205d4cf91..bd14c0872cb 100644
--- a/plugins/filebrowser/plugin.js
+++ b/plugins/filebrowser/plugin.js
@@ -297,42 +297,39 @@
 
 				if ( url ) {
 					var onClick = element.onClick;
+
+					// "element" here means the definition object, so we need to find the correct
+					// button to scope the event call
 					element.onClick = function( evt ) {
 						var sender = evt.sender;
 						var fileInput = sender.getDialog().getContentElement( this[ 'for' ][ 0 ], this[ 'for' ][ 1 ] ).getInputElement();
-						// Backward compatibility for IE8 and IE9 (https://cksource.tpondemand.com/entity/3117).
-						if ( editor.config.filebrowser_forceSubmit || !( CKEDITOR.plugins.clipboard && CKEDITOR.plugins.clipboard.isFileApiSupported ) ) {
-							// "element" here means the definition object, so we need to find the correct
-							// button to scope the event call
-							if ( onClick && onClick.call( sender, evt ) === false ) {
-								return false;
-							}
 
-							if ( uploadFile.call( sender, evt ) ) {
+						if ( onClick && onClick.call( sender, evt ) === false ) {
+							return false;
+						}
+
+						if ( uploadFile.call( sender, evt ) ) {
+
+							// Backward compatibility for IE8 and IE9 (https://cksource.tpondemand.com/entity/3117).
+							if ( editor.config.filebrowser_forceSubmit || !( CKEDITOR.plugins.clipboard && CKEDITOR.plugins.clipboard.isFileApiSupported ) ) {
 								// Append token preventing CSRF attacks.
 								appendToken( fileInput );
-								return true;
-							}
+								return 'form';
 
-							return false;
-						} else {
-							if ( uploadFile.call( sender, evt ) ) {
+							} else {
 								var loader = editor.uploadRepository.create( fileInput.$.files[ 0 ] );
-								// loader.loadAndUpload( sender.getDialog().getContentElement( this[ 'for' ][ 0 ], this[ 'for' ][ 1 ] ).action );
 
 								loader.on( 'uploaded', function( evt ) {
 									var response = evt.sender.responseData;
-
 									setUrl.call( evt.sender.editor, response.url, response.message );
-
 								} );
 
 								loader.loadAndUpload( CKEDITOR.fileTools.getUploadUrl( editor.config, 'image' ) );
-								// Return false to not trigger submit option in dialogui.
 
+								return 'xhr';
 							}
-							return false;
 						}
+						return false;
 					};
 
 					element.filebrowser.url = url;

From f3449bd661211e60449658bc535c19778ecd73b4 Mon Sep 17 00:00:00 2001
From: Mateusz Samsel <m.samsel@cksource.com>
Date: Wed, 13 Dec 2017 16:22:26 +0100
Subject: [PATCH 03/27] Unit test for adding XHR headers.

---
 tests/plugins/filetools/fileloader.js | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/tests/plugins/filetools/fileloader.js b/tests/plugins/filetools/fileloader.js
index 7a5d8ad0a5c..5a2ff27cf2e 100644
--- a/tests/plugins/filetools/fileloader.js
+++ b/tests/plugins/filetools/fileloader.js
@@ -14,7 +14,12 @@
 		testFile, lastFormData,
 		listeners = [],
 		editorMock = {
-			config: {}
+			config: {
+				xmlHttpRequestHeaders: {
+					foo: 'bar',
+					hello: 'world'
+				}
+			}
 		},
 		editorMockDefaultFileName = {
 			config: {
@@ -160,6 +165,11 @@
 						setTimeout( function() {
 							xhr.onabort();
 						}, 0 );
+					},
+
+					setRequestHeader: function( key, value ) {
+						this.requestHeaders = this.requestHeaders || {};
+						this.requestHeaders[ key ] = value;
 					}
 				};
 
@@ -1215,6 +1225,18 @@
 			loader.status = 'abort';
 
 			assert.isTrue( loader.isFinished() );
+		},
+
+		'text custom XHR headers': function() {
+			var loader = new FileLoader( editorMock, pngBase64 );
+
+			createXMLHttpRequestMock( [ 'load' ] );
+			loader.loadAndUpload( 'http://example.com' );
+
+			resumeAfter( loader, 'uploaded', function( evt ) {
+				objectAssert.areEqual( { 'foo': 'bar', 'hello': 'world' }, evt.sender.xhr.requestHeaders, 'XHR headers are not equal.' );
+			} );
+			wait();
 		}
 	} );
 } )();

From 56259abb46d449b4353649252d0d5c3120c1b7f3 Mon Sep 17 00:00:00 2001
From: Mateusz Samsel <m.samsel@cksource.com>
Date: Fri, 15 Dec 2017 11:45:05 +0100
Subject: [PATCH 04/27] Change condition to be independent from clipboard
 plugin.

---
 plugins/filebrowser/plugin.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/plugins/filebrowser/plugin.js b/plugins/filebrowser/plugin.js
index bd14c0872cb..e1ceea51e72 100644
--- a/plugins/filebrowser/plugin.js
+++ b/plugins/filebrowser/plugin.js
@@ -311,7 +311,7 @@
 						if ( uploadFile.call( sender, evt ) ) {
 
 							// Backward compatibility for IE8 and IE9 (https://cksource.tpondemand.com/entity/3117).
-							if ( editor.config.filebrowser_forceSubmit || !( CKEDITOR.plugins.clipboard && CKEDITOR.plugins.clipboard.isFileApiSupported ) ) {
+							if ( editor.config.filebrowser_forceSubmit || CKEDITOR.env.ie && CKEDITOR.env.version <= 9 ) {
 								// Append token preventing CSRF attacks.
 								appendToken( fileInput );
 								return 'form';

From b491787f546d78aa1c9820ad14de74271be5ec37 Mon Sep 17 00:00:00 2001
From: Mateusz Samsel <m.samsel@cksource.com>
Date: Fri, 15 Dec 2017 11:49:56 +0100
Subject: [PATCH 05/27] Unit test for uploading images.

---
 tests/plugins/filebrowser/uploadbutton.js | 138 ++++++++++++++++++++++
 1 file changed, 138 insertions(+)
 create mode 100644 tests/plugins/filebrowser/uploadbutton.js

diff --git a/tests/plugins/filebrowser/uploadbutton.js b/tests/plugins/filebrowser/uploadbutton.js
new file mode 100644
index 00000000000..23a96a70bb5
--- /dev/null
+++ b/tests/plugins/filebrowser/uploadbutton.js
@@ -0,0 +1,138 @@
+/* bender-tags: editor */
+/* bender-ckeditor-plugins: dialog,filebrowser,filetools,clipboard */
+
+( function() {
+	'use strict';
+
+	function mockInput( dialog, submit ) {
+		return sinon.stub( dialog, 'getContentElement', function() {
+			return {
+				getInputElement: function() {
+					return {
+						$: {
+							files: [
+								new File( [ '' ], 'sample.png' )
+							],
+							value: 'C:\\fakepath\\sample.gif',
+							form: ( new CKEDITOR.dom.element( 'form' ) ).$
+						}
+					};
+				},
+				getAction: function() {
+					return 'http://url-to-php-form';
+				},
+				submit: submit
+			};
+		} );
+	}
+
+	bender.editors = {
+		xhr: {
+			config: {
+				xmlHttpRequestHeaders: {
+					foo: 'bar',
+					hello: 'world'
+				},
+				filebrowserUploadUrl: 'foo'
+			}
+		},
+		submit: {
+			config: {
+				filebrowserUploadUrl: 'foo',
+				filebrowser_forceSubmit: true
+			}
+		}
+	};
+
+	CKEDITOR.on( 'instanceLoaded', function() {
+		CKEDITOR.dialog.add( 'testDialog', function() {
+			return {
+				title: 'Test Dialog',
+				contents: [
+					{
+						id: 'Upload',
+						hidden: true,
+						filebrowser: 'uploadButton',
+						label: 'Upload input',
+						elements: [ {
+							type: 'file',
+							id: 'upload',
+							label: 'Load file',
+							style: 'height:40px',
+							size: 38
+						},
+						{
+							type: 'fileButton',
+							id: 'uploadButton',
+							filebrowser: 'Upload:upload',
+							label: 'Send',
+							'for': [ 'Upload', 'upload' ]
+						} ]
+					}
+				]
+			};
+		} );
+	} );
+
+	bender.test( {
+		_should: {
+			ignore: {
+				'test for XHR request': CKEDITOR.env.ie && CKEDITOR.env.version < 9
+			}
+		},
+
+		setUp: function() {
+			this.xhr = sinon.useFakeXMLHttpRequest();
+			var requests = this.requests = [];
+
+			this.xhr.onCreate = function( xhr ) {
+				requests.push( xhr );
+			};
+		},
+
+		tearDown: function() {
+			this.xhr.restore();
+		},
+
+		'test for XHR request': function() {
+			var editor = this.editors.xhr,
+				bot = this.editorBots.xhr;
+
+			editor.addCommand( 'testDialog', new CKEDITOR.dialogCommand( 'testDialog' ) );
+			bot.dialog( 'testDialog', function( dialog ) {
+				var sendButton = dialog.getContentElement( 'Upload', 'uploadButton' );
+				var inputStub = mockInput( dialog );
+
+				// Execute just after XHR request is generated;
+				editor.on( 'fileUploadRequest', function() {
+					resume( function() {
+						arrayAssert.isNotEmpty( this.requests );
+						objectAssert.areEqual( { 'foo': 'bar', 'hello': 'world' }, this.requests[ 0 ].requestHeaders );
+						dialog.hide();
+						inputStub.restore();
+					} );
+				}, null, null, 1000 );
+
+				sendButton.click();
+				wait();
+			} );
+
+		},
+
+		'test for submit form': function() {
+			var editor = this.editors.submit,
+				bot = this.editorBots.submit;
+
+			editor.addCommand( 'testDialog', new CKEDITOR.dialogCommand( 'testDialog' ) );
+			bot.dialog( 'testDialog', function( dialog ) {
+				var sendButton = dialog.getContentElement( 'Upload', 'uploadButton' );
+				var mockSubmit = sinon.spy();
+				var inputStub = mockInput( dialog, mockSubmit );
+				sendButton.click();
+				assert.isTrue( mockSubmit.called, 'Submit method should be used.' );
+				inputStub.restore();
+				dialog.hide();
+			} );
+		}
+	} );
+} )();

From 156fb1087c20508bae161a3488b7a7236486db03 Mon Sep 17 00:00:00 2001
From: Mateusz Samsel <m.samsel@cksource.com>
Date: Fri, 15 Dec 2017 12:52:24 +0100
Subject: [PATCH 06/27] Rename config flag, add docs.

---
 plugins/filebrowser/plugin.js             | 11 ++++++++++-
 tests/plugins/filebrowser/uploadbutton.js |  2 +-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/plugins/filebrowser/plugin.js b/plugins/filebrowser/plugin.js
index e1ceea51e72..a3c44e7f0c4 100644
--- a/plugins/filebrowser/plugin.js
+++ b/plugins/filebrowser/plugin.js
@@ -311,7 +311,7 @@
 						if ( uploadFile.call( sender, evt ) ) {
 
 							// Backward compatibility for IE8 and IE9 (https://cksource.tpondemand.com/entity/3117).
-							if ( editor.config.filebrowser_forceSubmit || CKEDITOR.env.ie && CKEDITOR.env.version <= 9 ) {
+							if ( editor.config.filebrowser_forceFormSubmit || CKEDITOR.env.ie && CKEDITOR.env.version <= 9 ) {
 								// Append token preventing CSRF attacks.
 								appendToken( fileInput );
 								return 'form';
@@ -588,3 +588,12 @@
  * @cfg {Number/String} [filebrowserWindowHeight='70%']
  * @member CKEDITOR.config
  */
+
+/**
+ * Force filebrowser plugin to use form submit action instead of XHR request when file is uploaded in dialogs.
+ *
+ * 		config.filebrowser_forceFormSubmit = true
+ *
+ * @cfg {Boolean} [filebrowser_forceFormSubmit=false]
+ * @member CKEDITOR.config
+ */
diff --git a/tests/plugins/filebrowser/uploadbutton.js b/tests/plugins/filebrowser/uploadbutton.js
index 23a96a70bb5..1b0ddcd0f1a 100644
--- a/tests/plugins/filebrowser/uploadbutton.js
+++ b/tests/plugins/filebrowser/uploadbutton.js
@@ -39,7 +39,7 @@
 		submit: {
 			config: {
 				filebrowserUploadUrl: 'foo',
-				filebrowser_forceSubmit: true
+				filebrowser_forceFormSubmit: true
 			}
 		}
 	};

From ef08686166acb2f47bcadd479b27110bc269d9bb Mon Sep 17 00:00:00 2001
From: Mateusz Samsel <m.samsel@cksource.com>
Date: Fri, 15 Dec 2017 16:34:15 +0100
Subject: [PATCH 07/27] Code optimization, adding feature detection for file
 uploading.

---
 plugins/dialogui/plugin.js            |  6 +++---
 plugins/filebrowser/plugin.js         |  3 +--
 plugins/filetools/plugin.js           | 26 ++++++++++++++++++++++----
 tests/plugins/filetools/fileloader.js | 12 +++++++-----
 4 files changed, 33 insertions(+), 14 deletions(-)

diff --git a/plugins/dialogui/plugin.js b/plugins/dialogui/plugin.js
index fdf08c7cff8..474b97133fe 100644
--- a/plugins/dialogui/plugin.js
+++ b/plugins/dialogui/plugin.js
@@ -745,10 +745,10 @@ CKEDITOR.plugins.add( 'dialogui', {
 					var target = elementDefinition[ 'for' ]; // [ pageId, elementId ]
 
 					// If exists onClick in elementDefinition, then it is called and checked response type.
-					// If it's posiblle, then XHR is used, what prevents of using submit.
-					var responseType = onClick && onClick.call( this, evt );
+					// If it's possible, then XHR is used, what prevents of using submit.
+					var responseType = onClick ? onClick.call( this, evt ) : false;
 
-					if ( !onClick || responseType !== false ) {
+					if ( responseType !== false ) {
 						if ( responseType === 'form' ) {
 							dialog.getContentElement( target[ 0 ], target[ 1 ] ).submit();
 						}
diff --git a/plugins/filebrowser/plugin.js b/plugins/filebrowser/plugin.js
index a3c44e7f0c4..305bc95b9e9 100644
--- a/plugins/filebrowser/plugin.js
+++ b/plugins/filebrowser/plugin.js
@@ -309,9 +309,8 @@
 						}
 
 						if ( uploadFile.call( sender, evt ) ) {
-
 							// Backward compatibility for IE8 and IE9 (https://cksource.tpondemand.com/entity/3117).
-							if ( editor.config.filebrowser_forceFormSubmit || CKEDITOR.env.ie && CKEDITOR.env.version <= 9 ) {
+							if ( editor.config.filebrowser_forceFormSubmit || !CKEDITOR.fileTools.isFileUploadSupported ) {
 								// Append token preventing CSRF attacks.
 								appendToken( fileInput );
 								return 'form';
diff --git a/plugins/filetools/plugin.js b/plugins/filetools/plugin.js
index 953262da248..f5201fefae0 100644
--- a/plugins/filetools/plugin.js
+++ b/plugins/filetools/plugin.js
@@ -49,6 +49,7 @@
 				var fileLoader = evt.data.fileLoader,
 					$formData = new FormData(),
 					requestData = evt.data.requestData,
+					configXHRHeaders = editor.config.xmlHttpRequestHeaders,
 					header;
 
 				for ( var name in requestData ) {
@@ -65,9 +66,9 @@
 				// Append token preventing CSRF attacks.
 				$formData.append( 'ckCsrfToken', CKEDITOR.tools.getCsrfToken() );
 
-				if ( editor.config.xmlHttpRequestHeaders ) {
-					for ( header in editor.config.xmlHttpRequestHeaders ) {
-						fileLoader.xhr.setRequestHeader( header, editor.config.xmlHttpRequestHeaders[ header ] );
+				if ( configXHRHeaders ) {
+					for ( header in configXHRHeaders ) {
+						fileLoader.xhr.setRequestHeader( header, configXHRHeaders[ header ] );
 					}
 				}
 
@@ -863,7 +864,24 @@
 		 */
 		isTypeSupported: function( file, supportedTypes ) {
 			return !!file.type.match( supportedTypes );
-		}
+		},
+
+		/**
+		 * Property inform if current browser poses native methods used by {@link CKEDITOR.fileTools} to upload files.
+		 *
+		 * @property {Boolean} isFileUploadSupported
+		 */
+		isFileUploadSupported: ( function() {
+			if ( typeof FileReader === 'function' &&
+				typeof ( new FileReader() ).readAsDataURL === 'function' &&
+				typeof FormData === 'function' &&
+				typeof ( new FormData() ).append === 'function' &&
+				typeof XMLHttpRequest === 'function' && typeof Blob === 'function' ) {
+
+				return true;
+			}
+			return false;
+		} )()
 	} );
 } )();
 
diff --git a/tests/plugins/filetools/fileloader.js b/tests/plugins/filetools/fileloader.js
index 5a2ff27cf2e..27468cdb653 100644
--- a/tests/plugins/filetools/fileloader.js
+++ b/tests/plugins/filetools/fileloader.js
@@ -167,10 +167,7 @@
 						}, 0 );
 					},
 
-					setRequestHeader: function( key, value ) {
-						this.requestHeaders = this.requestHeaders || {};
-						this.requestHeaders[ key ] = value;
-					}
+					setRequestHeader: sinon.stub()
 				};
 
 			return xhr;
@@ -1234,7 +1231,12 @@
 			loader.loadAndUpload( 'http://example.com' );
 
 			resumeAfter( loader, 'uploaded', function( evt ) {
-				objectAssert.areEqual( { 'foo': 'bar', 'hello': 'world' }, evt.sender.xhr.requestHeaders, 'XHR headers are not equal.' );
+				var setRequestHeaderStub = evt.sender.xhr.setRequestHeader;
+
+				sinon.assert.calledWithExactly( setRequestHeaderStub, 'foo', 'bar' );
+				sinon.assert.calledWithExactly( setRequestHeaderStub, 'hello', 'world' );
+
+				assert.areSame( 2, setRequestHeaderStub.callCount, 'setRequestHeader call count' );
 			} );
 			wait();
 		}

From ccfffa1dec5040419fc2fbff4c451b449899123c Mon Sep 17 00:00:00 2001
From: Mateusz Samsel <m.samsel@cksource.com>
Date: Fri, 15 Dec 2017 16:57:37 +0100
Subject: [PATCH 08/27] Preserve backward compatybility with returned data
 formats.

---
 plugins/dialogui/plugin.js    | 2 +-
 plugins/filebrowser/plugin.js | 4 ++--
 plugins/filetools/plugin.js   | 3 ++-
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/plugins/dialogui/plugin.js b/plugins/dialogui/plugin.js
index 474b97133fe..75cfb12fddd 100644
--- a/plugins/dialogui/plugin.js
+++ b/plugins/dialogui/plugin.js
@@ -749,7 +749,7 @@ CKEDITOR.plugins.add( 'dialogui', {
 					var responseType = onClick ? onClick.call( this, evt ) : false;
 
 					if ( responseType !== false ) {
-						if ( responseType === 'form' ) {
+						if ( responseType !== 'xhr' ) {
 							dialog.getContentElement( target[ 0 ], target[ 1 ] ).submit();
 						}
 						this.disable();
diff --git a/plugins/filebrowser/plugin.js b/plugins/filebrowser/plugin.js
index 305bc95b9e9..a9d682308dc 100644
--- a/plugins/filebrowser/plugin.js
+++ b/plugins/filebrowser/plugin.js
@@ -313,7 +313,7 @@
 							if ( editor.config.filebrowser_forceFormSubmit || !CKEDITOR.fileTools.isFileUploadSupported ) {
 								// Append token preventing CSRF attacks.
 								appendToken( fileInput );
-								return 'form';
+								return true;
 
 							} else {
 								var loader = editor.uploadRepository.create( fileInput.$.files[ 0 ] );
@@ -323,7 +323,7 @@
 									setUrl.call( evt.sender.editor, response.url, response.message );
 								} );
 
-								loader.loadAndUpload( CKEDITOR.fileTools.getUploadUrl( editor.config, 'image' ) );
+								loader.loadAndUpload( url );
 
 								return 'xhr';
 							}
diff --git a/plugins/filetools/plugin.js b/plugins/filetools/plugin.js
index f5201fefae0..b1f37ef711f 100644
--- a/plugins/filetools/plugin.js
+++ b/plugins/filetools/plugin.js
@@ -876,7 +876,8 @@
 				typeof ( new FileReader() ).readAsDataURL === 'function' &&
 				typeof FormData === 'function' &&
 				typeof ( new FormData() ).append === 'function' &&
-				typeof XMLHttpRequest === 'function' && typeof Blob === 'function' ) {
+				typeof XMLHttpRequest === 'function' &&
+				typeof Blob === 'function' ) {
 
 				return true;
 			}

From 9642a81e7ba444cc639fc16747658ba3e4a83d90 Mon Sep 17 00:00:00 2001
From: Mateusz Samsel <m.samsel@cksource.com>
Date: Mon, 18 Dec 2017 09:16:54 +0100
Subject: [PATCH 09/27] Little changes in unit tests.

---
 tests/plugins/filebrowser/uploadbutton.js | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/tests/plugins/filebrowser/uploadbutton.js b/tests/plugins/filebrowser/uploadbutton.js
index 1b0ddcd0f1a..e8edb59f85f 100644
--- a/tests/plugins/filebrowser/uploadbutton.js
+++ b/tests/plugins/filebrowser/uploadbutton.js
@@ -100,8 +100,8 @@
 
 			editor.addCommand( 'testDialog', new CKEDITOR.dialogCommand( 'testDialog' ) );
 			bot.dialog( 'testDialog', function( dialog ) {
-				var sendButton = dialog.getContentElement( 'Upload', 'uploadButton' );
-				var inputStub = mockInput( dialog );
+				var sendButton = dialog.getContentElement( 'Upload', 'uploadButton' ),
+					inputStub = mockInput( dialog );
 
 				// Execute just after XHR request is generated;
 				editor.on( 'fileUploadRequest', function() {
@@ -116,7 +116,6 @@
 				sendButton.click();
 				wait();
 			} );
-
 		},
 
 		'test for submit form': function() {
@@ -125,9 +124,10 @@
 
 			editor.addCommand( 'testDialog', new CKEDITOR.dialogCommand( 'testDialog' ) );
 			bot.dialog( 'testDialog', function( dialog ) {
-				var sendButton = dialog.getContentElement( 'Upload', 'uploadButton' );
-				var mockSubmit = sinon.spy();
-				var inputStub = mockInput( dialog, mockSubmit );
+				var sendButton = dialog.getContentElement( 'Upload', 'uploadButton' ),
+					mockSubmit = sinon.spy(),
+					inputStub = mockInput( dialog, mockSubmit );
+
 				sendButton.click();
 				assert.isTrue( mockSubmit.called, 'Submit method should be used.' );
 				inputStub.restore();

From 5fcd547e96b9c203f10ad680c3337bd001f14e68 Mon Sep 17 00:00:00 2001
From: Mateusz Samsel <m.samsel@cksource.com>
Date: Mon, 18 Dec 2017 11:06:10 +0100
Subject: [PATCH 10/27] Manual tests for XHR upload.

---
 .../plugins/filebrowser/manual/uploadxhr.html | 50 +++++++++++++++++++
 tests/plugins/filebrowser/manual/uploadxhr.md | 18 +++++++
 2 files changed, 68 insertions(+)
 create mode 100644 tests/plugins/filebrowser/manual/uploadxhr.html
 create mode 100644 tests/plugins/filebrowser/manual/uploadxhr.md

diff --git a/tests/plugins/filebrowser/manual/uploadxhr.html b/tests/plugins/filebrowser/manual/uploadxhr.html
new file mode 100644
index 00000000000..aa0d9f1a3e5
--- /dev/null
+++ b/tests/plugins/filebrowser/manual/uploadxhr.html
@@ -0,0 +1,50 @@
+<textarea id="classic">
+
+</textarea>
+
+<div id="output" style="background-color:lightgreen;"></div>
+
+<script>
+	var xhr, requests;
+
+	CKEDITOR.on( 'instanceLoaded', function() {
+		if ( !CKEDITOR.fileTools.isFileUploadSupported ) {
+			bender.ignore();
+		} else {
+			// Mock XHR
+			xhr = sinon.useFakeXMLHttpRequest();
+			requests = [];
+			xhr.onCreate = function( xhr ) {
+				requests.push( xhr );
+			};
+			window.onunload = function() {
+				xhr.restore();
+				server.restore();
+			}
+		}
+	} );
+
+	var classic = CKEDITOR.replace( 'classic', {
+		xmlHttpRequestHeaders: {
+			'hello': 'world',
+			'foo': 'bar'
+		},
+		filebrowserUploadUrl: 'fake-url'
+	} );
+
+	// Display XHR details when CKEDITOR process entire request.
+	classic.on( 'fileUploadRequest', function( evt ) {
+		var output = document.getElementById( 'output' );
+		var outputString = CKEDITOR.tools.array.reduce( requests, function( acc, item ) {
+			var line = '';
+			for ( header in item.requestHeaders ) {
+				if ( item.requestHeaders.hasOwnProperty( header ) ) {
+					line += '| <code>header: ' + header + ', value: ' + item.requestHeaders[ header ] + '</code> |';
+				}
+			}
+			acc += '<li>' + line + '</li>';
+			return acc;
+		}, '' );
+		output.innerHTML = '<ol>' + outputString + '</ol>';
+	}, null, null, 1000 )
+</script>
diff --git a/tests/plugins/filebrowser/manual/uploadxhr.md b/tests/plugins/filebrowser/manual/uploadxhr.md
new file mode 100644
index 00000000000..5bed918ec64
--- /dev/null
+++ b/tests/plugins/filebrowser/manual/uploadxhr.md
@@ -0,0 +1,18 @@
+@bender-tags: 4.8.1, feature, tp3117
+@bender-ui: collapsed
+@bender-ckeditor-plugins: wysiwygarea, toolbar, filebrowser, filetools, image, link, flash
+
+----
+1. Open image dialog
+2. Go to upload tab
+3. Select some image and send it to server
+4. Close dialog (There might appear warning that image url is not set up)
+
+Repeat those steps for Link and Flash plugin.
+
+_Note:_ When new upload request is made, it should be visible as separate line below.
+
+**Expected:** Below editor will appear green div with listed headers attempted to send. There are 2 headers in single line:
+`hello: world, foo: bar`.
+
+**Unexpected:** Headers are not listed below.

From 998568048a42c48f7c1c37b9b49c0e3c491597fa Mon Sep 17 00:00:00 2001
From: Mateusz Samsel <m.samsel@cksource.com>
Date: Tue, 19 Dec 2017 18:49:53 +0100
Subject: [PATCH 11/27] Review fixes: chnage in behaviour to have 'form' as
 default action, big changes to docs related to the feature.

---
 plugins/filebrowser/plugin.js                 | 23 ++++++++++---
 plugins/filetools/plugin.js                   | 13 ++++++++
 .../plugins/filebrowser/manual/uploadxhr.html | 33 +++++++++----------
 3 files changed, 48 insertions(+), 21 deletions(-)

diff --git a/plugins/filebrowser/plugin.js b/plugins/filebrowser/plugin.js
index a9d682308dc..35c2b7c5508 100644
--- a/plugins/filebrowser/plugin.js
+++ b/plugins/filebrowser/plugin.js
@@ -310,7 +310,8 @@
 
 						if ( uploadFile.call( sender, evt ) ) {
 							// Backward compatibility for IE8 and IE9 (https://cksource.tpondemand.com/entity/3117).
-							if ( editor.config.filebrowser_forceFormSubmit || !CKEDITOR.fileTools.isFileUploadSupported ) {
+							// With version 4.9.0 change: `!== 'xhr'` to `=== 'form'`.
+							if ( editor.config.filebrowserUploadMethod !== 'xhr' || !( CKEDITOR.fileTools && CKEDITOR.fileTools.isFileUploadSupported ) ) {
 								// Append token preventing CSRF attacks.
 								appendToken( fileInput );
 								return true;
@@ -589,10 +590,24 @@
  */
 
 /**
- * Force filebrowser plugin to use form submit action instead of XHR request when file is uploaded in dialogs.
+ * Define preferred option to submit file upload with filebrowser plugin. If value is not specified,
+ * `'form'` option is used. Additional XHR headers might be set up with {@link CKEDITOR.config#xmlHttpRequestHeaders}.
  *
- * 		config.filebrowser_forceFormSubmit = true
+ * Available values:
  *
- * @cfg {Boolean} [filebrowser_forceFormSubmit=false]
+ *	* `'xhr'` - XMLHttpRequest is used to upload file
+ *	* `'form'` - Form submit is used to upload file
+ *	* `undefiend` - when configuration option is not specified `'form'` configuration is used
+ *
+ * Note: please be aware that `'xhr'` requires {@link CKEDITOR.fileTools} for proper work. Missing this plugins
+ * or using browsers which isn't supported {@link CKEDITOR.fileTools#isFileUploadSupported},
+ * will force using `'form'` behaviour despite configuration option.
+ *
+ * 	// Modern browsers will use XMLHttpRequest to upload files.
+ * 	// IE8 and IE9 will use form submit even tough config option is set to 'xhr'.
+ * 	config.filebrowserUploadMethod = 'xhr';
+ *
+ * @since 4.8.1
+ * @cfg {Boolean} [filebrowserUploadMethod=undefined]
  * @member CKEDITOR.config
  */
diff --git a/plugins/filetools/plugin.js b/plugins/filetools/plugin.js
index b1f37ef711f..ba4e0254dcc 100644
--- a/plugins/filetools/plugin.js
+++ b/plugins/filetools/plugin.js
@@ -911,3 +911,16 @@
  * @cfg {String} [fileTools_defaultFileName='']
  * @member CKEDITOR.config
  */
+
+/**
+ * Additional headers of XMLHttpRequest used during file upload with plugins: {@link CKEDITOR.fileTools} and filebrowser.
+ *
+ * 	config.xmlHttpRequestHeaders = {
+ * 		'Cache-Control': 'no-cache',
+ * 		'X-CUSTOM': 'HEADER'
+ * 	};
+ *
+ * @since 4.8.1
+ * @cfg {Object} [xmlHttpRequestHeaders=null]
+ * @member CKEDITOR.config
+ */
diff --git a/tests/plugins/filebrowser/manual/uploadxhr.html b/tests/plugins/filebrowser/manual/uploadxhr.html
index aa0d9f1a3e5..ca69964eb97 100644
--- a/tests/plugins/filebrowser/manual/uploadxhr.html
+++ b/tests/plugins/filebrowser/manual/uploadxhr.html
@@ -7,29 +7,28 @@
 <script>
 	var xhr, requests;
 
-	CKEDITOR.on( 'instanceLoaded', function() {
-		if ( !CKEDITOR.fileTools.isFileUploadSupported ) {
-			bender.ignore();
-		} else {
-			// Mock XHR
-			xhr = sinon.useFakeXMLHttpRequest();
-			requests = [];
-			xhr.onCreate = function( xhr ) {
-				requests.push( xhr );
-			};
-			window.onunload = function() {
-				xhr.restore();
-				server.restore();
-			}
+	if ( CKEDITOR.env.ie && CKEDITOR.env.version < 10 ) {
+		bender.ignore();
+	} else {
+		// Mock XHR
+		xhr = sinon.useFakeXMLHttpRequest();
+		requests = [];
+		xhr.onCreate = function( xhr ) {
+			requests.push( xhr );
+		};
+		window.onunload = function() {
+			xhr.restore();
+			server.restore();
 		}
-	} );
+	}
 
 	var classic = CKEDITOR.replace( 'classic', {
 		xmlHttpRequestHeaders: {
 			'hello': 'world',
 			'foo': 'bar'
 		},
-		filebrowserUploadUrl: 'fake-url'
+		filebrowserUploadUrl: 'fake-url',
+		filebrowserUploadMethod: 'xhr'
 	} );
 
 	// Display XHR details when CKEDITOR process entire request.
@@ -39,7 +38,7 @@
 			var line = '';
 			for ( header in item.requestHeaders ) {
 				if ( item.requestHeaders.hasOwnProperty( header ) ) {
-					line += '| <code>header: ' + header + ', value: ' + item.requestHeaders[ header ] + '</code> |';
+					line += ' | <code>header: ' + header + ', value: ' + item.requestHeaders[ header ] + '</code> |';
 				}
 			}
 			acc += '<li>' + line + '</li>';

From 4cd6c1f6aca152e5a36388585f662ad0fe37c2fb Mon Sep 17 00:00:00 2001
From: Mateusz Samsel <m.samsel@cksource.com>
Date: Wed, 20 Dec 2017 11:49:06 +0100
Subject: [PATCH 12/27] Review fixes: add error handling to loader, provide
 extra unit and manual test, code clean up.

---
 plugins/filebrowser/plugin.js                 | 11 +++
 .../plugins/filebrowser/manual/uploadxhr.html |  1 -
 .../manual/uploadxhrwitherror.html            | 18 +++++
 .../filebrowser/manual/uploadxhrwitherror.md  | 16 ++++
 tests/plugins/filebrowser/uploadbutton.js     | 80 ++++++++++++++++++-
 5 files changed, 121 insertions(+), 5 deletions(-)
 create mode 100644 tests/plugins/filebrowser/manual/uploadxhrwitherror.html
 create mode 100644 tests/plugins/filebrowser/manual/uploadxhrwitherror.md

diff --git a/plugins/filebrowser/plugin.js b/plugins/filebrowser/plugin.js
index 35c2b7c5508..d362b09c5da 100644
--- a/plugins/filebrowser/plugin.js
+++ b/plugins/filebrowser/plugin.js
@@ -324,6 +324,11 @@
 									setUrl.call( evt.sender.editor, response.url, response.message );
 								} );
 
+								// Return non-false value will disable fileButton in dialogui,
+								// below listeners takes care of such situation and re-enable "send" button.
+								loader.on( 'error', xhrUploadErrorHandler.bind( this ) );
+								loader.on( 'abort', xhrUploadErrorHandler.bind( this ) );
+
 								loader.loadAndUpload( url );
 
 								return 'xhr';
@@ -340,6 +345,12 @@
 		}
 	}
 
+	function xhrUploadErrorHandler( evt ) {
+		// `this` is a reference to ui.dialog.fileButton.
+		this.enable();
+		alert( evt.sender.message ); // jshint ignore:line
+	}
+
 	// Updates the target element with the url of uploaded/selected file.
 	//
 	// @param {String}
diff --git a/tests/plugins/filebrowser/manual/uploadxhr.html b/tests/plugins/filebrowser/manual/uploadxhr.html
index ca69964eb97..3612e0241ad 100644
--- a/tests/plugins/filebrowser/manual/uploadxhr.html
+++ b/tests/plugins/filebrowser/manual/uploadxhr.html
@@ -18,7 +18,6 @@
 		};
 		window.onunload = function() {
 			xhr.restore();
-			server.restore();
 		}
 	}
 
diff --git a/tests/plugins/filebrowser/manual/uploadxhrwitherror.html b/tests/plugins/filebrowser/manual/uploadxhrwitherror.html
new file mode 100644
index 00000000000..98263162616
--- /dev/null
+++ b/tests/plugins/filebrowser/manual/uploadxhrwitherror.html
@@ -0,0 +1,18 @@
+<textarea id="classic">
+
+</textarea>
+
+<div id="output" style="background-color:lightgreen;"></div>
+
+<script>
+	var xhr, requests;
+
+	if ( CKEDITOR.env.ie && CKEDITOR.env.version < 10 ) {
+		bender.ignore();
+	}
+
+	var classic = CKEDITOR.replace( 'classic', {
+		filebrowserUploadUrl: 'fake-url',
+		filebrowserUploadMethod: 'xhr'
+	} );
+</script>
diff --git a/tests/plugins/filebrowser/manual/uploadxhrwitherror.md b/tests/plugins/filebrowser/manual/uploadxhrwitherror.md
new file mode 100644
index 00000000000..25a26d63591
--- /dev/null
+++ b/tests/plugins/filebrowser/manual/uploadxhrwitherror.md
@@ -0,0 +1,16 @@
+@bender-tags: 4.8.1, feature, tp3117
+@bender-ui: collapsed
+@bender-ckeditor-plugins: wysiwygarea, toolbar, filebrowser, filetools, image, link, flash
+
+----
+1. Open image dialog
+2. Go to upload tab
+3. Select some image and send it to server
+4. **Alert** should be displayed
+5. Try to upload file again
+
+Repeat those steps for Link and Flash plugin.
+
+**Expected:** After first upload attempt, send button is enabled. Which means that every next click trigger new uploading process and generate new alert message.
+
+**Unexpected:** After first upload send button is disabled. Second and further upload attempts don't trigger upload process, and alert is not shown.
diff --git a/tests/plugins/filebrowser/uploadbutton.js b/tests/plugins/filebrowser/uploadbutton.js
index e8edb59f85f..c818a2a80ab 100644
--- a/tests/plugins/filebrowser/uploadbutton.js
+++ b/tests/plugins/filebrowser/uploadbutton.js
@@ -33,13 +33,15 @@
 					foo: 'bar',
 					hello: 'world'
 				},
-				filebrowserUploadUrl: 'foo'
+				filebrowserUploadUrl: 'foo',
+				filebrowserUploadMethod: 'xhr',
+				lang: 'en'
 			}
 		},
 		submit: {
 			config: {
 				filebrowserUploadUrl: 'foo',
-				filebrowser_forceFormSubmit: true
+				filebrowserUploadMethod: 'form'
 			}
 		}
 	};
@@ -94,7 +96,7 @@
 			this.xhr.restore();
 		},
 
-		'test for XHR request': function() {
+		'test for xhr request': function() {
 			var editor = this.editors.xhr,
 				bot = this.editorBots.xhr;
 
@@ -104,7 +106,7 @@
 					inputStub = mockInput( dialog );
 
 				// Execute just after XHR request is generated;
-				editor.on( 'fileUploadRequest', function() {
+				editor.once( 'fileUploadRequest', function() {
 					resume( function() {
 						arrayAssert.isNotEmpty( this.requests );
 						objectAssert.areEqual( { 'foo': 'bar', 'hello': 'world' }, this.requests[ 0 ].requestHeaders );
@@ -133,6 +135,76 @@
 				inputStub.restore();
 				dialog.hide();
 			} );
+		},
+
+		'test for xhr loader error': function() {
+			var editor = this.editors.xhr,
+				bot = this.editorBots.xhr;
+
+			editor.addCommand( 'testDialog', new CKEDITOR.dialogCommand( 'testDialog' ) );
+			bot.dialog( 'testDialog', function( dialog ) {
+				var sendButton = dialog.getContentElement( 'Upload', 'uploadButton' ),
+					inputStub = mockInput( dialog );
+
+				var alertStub = sinon.stub( window, 'alert' );
+
+				editor.once( 'fileUploadRequest', function( evt ) {
+					var loader = evt.data.fileLoader;
+					loader.once( 'error', function() {
+						resume( function() {
+							sinon.assert.calledWithExactly( alertStub, 'HTTP error occurred during file upload (403: Forbidden).' );
+							assert.isTrue( sendButton.isEnabled(), 'Button should be enabled after error' );
+
+							dialog.hide();
+							inputStub.restore();
+							alertStub.restore();
+						} );
+					} );
+
+					assert.isFalse( sendButton.isEnabled(), 'Button should be disabled during upload' );
+
+					// Simulate loading error
+					loader.xhr.status = 403;
+					loader.xhr.onload();
+				} );
+
+				sendButton.click();
+				wait();
+			} );
+		},
+
+		'test for xhr loader abort': function() {
+			var editor = this.editors.xhr,
+				bot = this.editorBots.xhr;
+
+			editor.addCommand( 'testDialog', new CKEDITOR.dialogCommand( 'testDialog' ) );
+			bot.dialog( 'testDialog', function( dialog ) {
+				var sendButton = dialog.getContentElement( 'Upload', 'uploadButton' ),
+					inputStub = mockInput( dialog );
+
+				var alertStub = sinon.stub( window, 'alert' );
+
+				editor.once( 'fileUploadRequest', function( evt ) {
+					var loader = evt.data.fileLoader;
+					loader.once( 'abort', function() {
+						resume( function() {
+							assert.isTrue( alertStub.called, 'Abort message should appear' );
+							assert.isTrue( sendButton.isEnabled(), 'Button should be enabled after abort' );
+
+							dialog.hide();
+							inputStub.restore();
+							alertStub.restore();
+						} );
+					} );
+
+					assert.isFalse( sendButton.isEnabled(), 'Button should be disabled during upload' );
+
+					loader.changeStatus( 'abort' );
+				} );
+
+				sendButton.click();
+				wait();
+			} );
 		}
 	} );
 } )();

From f9f54df477f58fc6e3d5bdab25907fb96a06c95b Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Wed, 20 Dec 2017 15:40:19 +0100
Subject: [PATCH 13/27] Simplified file upload api detection.

---
 plugins/filebrowser/plugin.js | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/plugins/filebrowser/plugin.js b/plugins/filebrowser/plugin.js
index d362b09c5da..40c68bd44af 100644
--- a/plugins/filebrowser/plugin.js
+++ b/plugins/filebrowser/plugin.js
@@ -301,8 +301,9 @@
 					// "element" here means the definition object, so we need to find the correct
 					// button to scope the event call
 					element.onClick = function( evt ) {
-						var sender = evt.sender;
-						var fileInput = sender.getDialog().getContentElement( this[ 'for' ][ 0 ], this[ 'for' ][ 1 ] ).getInputElement();
+						var sender = evt.sender,
+							fileInput = sender.getDialog().getContentElement( this[ 'for' ][ 0 ], this[ 'for' ][ 1 ] ).getInputElement(),
+							isFileUploadApiSupported = CKEDITOR.fileTools && CKEDITOR.fileTools.isFileUploadSupported;
 
 						if ( onClick && onClick.call( sender, evt ) === false ) {
 							return false;
@@ -311,7 +312,7 @@
 						if ( uploadFile.call( sender, evt ) ) {
 							// Backward compatibility for IE8 and IE9 (https://cksource.tpondemand.com/entity/3117).
 							// With version 4.9.0 change: `!== 'xhr'` to `=== 'form'`.
-							if ( editor.config.filebrowserUploadMethod !== 'xhr' || !( CKEDITOR.fileTools && CKEDITOR.fileTools.isFileUploadSupported ) ) {
+							if ( editor.config.filebrowserUploadMethod !== 'xhr' || !isFileUploadApiSupported ) {
 								// Append token preventing CSRF attacks.
 								appendToken( fileInput );
 								return true;

From 40a1d06b0afbaa53a67a4f54bbc8cec90dab72cf Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Wed, 20 Dec 2017 15:59:44 +0100
Subject: [PATCH 14/27] Test: simplified manual test for xhr upload in
 filebrowser plugin.

---
 .../plugins/filebrowser/manual/uploadxhr.html | 25 +++++++------------
 tests/plugins/filebrowser/manual/uploadxhr.md | 10 ++++----
 2 files changed, 14 insertions(+), 21 deletions(-)

diff --git a/tests/plugins/filebrowser/manual/uploadxhr.html b/tests/plugins/filebrowser/manual/uploadxhr.html
index 3612e0241ad..e548952fbc5 100644
--- a/tests/plugins/filebrowser/manual/uploadxhr.html
+++ b/tests/plugins/filebrowser/manual/uploadxhr.html
@@ -1,11 +1,10 @@
-<textarea id="classic">
+<textarea id="classic"></textarea>
 
-</textarea>
-
-<div id="output" style="background-color:lightgreen;"></div>
+<pre id="output" style="background-color:lightgreen;"></pre>
 
 <script>
-	var xhr, requests;
+	var xhr,
+		requests;
 
 	if ( CKEDITOR.env.ie && CKEDITOR.env.version < 10 ) {
 		bender.ignore();
@@ -32,17 +31,11 @@
 
 	// Display XHR details when CKEDITOR process entire request.
 	classic.on( 'fileUploadRequest', function( evt ) {
-		var output = document.getElementById( 'output' );
-		var outputString = CKEDITOR.tools.array.reduce( requests, function( acc, item ) {
-			var line = '';
-			for ( header in item.requestHeaders ) {
-				if ( item.requestHeaders.hasOwnProperty( header ) ) {
-					line += ' | <code>header: ' + header + ', value: ' + item.requestHeaders[ header ] + '</code> |';
-				}
-			}
-			acc += '<li>' + line + '</li>';
-			return acc;
-		}, '' );
+		var output = document.getElementById( 'output' ),
+			outputString = CKEDITOR.tools.array.reduce( requests, function( acc, item ) {
+				return acc + '<li>' + JSON.stringify( item.requestHeaders, null, 4 ) + '</li>';
+			}, '' );
+
 		output.innerHTML = '<ol>' + outputString + '</ol>';
 	}, null, null, 1000 )
 </script>
diff --git a/tests/plugins/filebrowser/manual/uploadxhr.md b/tests/plugins/filebrowser/manual/uploadxhr.md
index 5bed918ec64..17ba12f107a 100644
--- a/tests/plugins/filebrowser/manual/uploadxhr.md
+++ b/tests/plugins/filebrowser/manual/uploadxhr.md
@@ -1,4 +1,4 @@
-@bender-tags: 4.8.1, feature, tp3117
+@bender-tags: 4.8.1, feature, 643, tp3117
 @bender-ui: collapsed
 @bender-ckeditor-plugins: wysiwygarea, toolbar, filebrowser, filetools, image, link, flash
 
@@ -8,11 +8,11 @@
 3. Select some image and send it to server
 4. Close dialog (There might appear warning that image url is not set up)
 
-Repeat those steps for Link and Flash plugin.
-
-_Note:_ When new upload request is made, it should be visible as separate line below.
-
 **Expected:** Below editor will appear green div with listed headers attempted to send. There are 2 headers in single line:
 `hello: world, foo: bar`.
 
 **Unexpected:** Headers are not listed below.
+
+Repeat those steps for Link and Flash plugin.
+
+_Note:_ When a new upload request is made, it should be visible as a separate line below.
\ No newline at end of file

From d2da1809fef5135121eb9bc4f787c32c8912e3a3 Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Wed, 20 Dec 2017 16:07:12 +0100
Subject: [PATCH 15/27] Tests: adjusted manual tests for 404 errors using XHR
 in filebrowser plugin.

---
 .../filebrowser/manual/uploadxhrwitherror.html   |  5 +----
 .../filebrowser/manual/uploadxhrwitherror.md     | 16 +++++++++-------
 2 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/tests/plugins/filebrowser/manual/uploadxhrwitherror.html b/tests/plugins/filebrowser/manual/uploadxhrwitherror.html
index 98263162616..944862873b7 100644
--- a/tests/plugins/filebrowser/manual/uploadxhrwitherror.html
+++ b/tests/plugins/filebrowser/manual/uploadxhrwitherror.html
@@ -1,17 +1,14 @@
 <textarea id="classic">
-
 </textarea>
 
 <div id="output" style="background-color:lightgreen;"></div>
 
 <script>
-	var xhr, requests;
-
 	if ( CKEDITOR.env.ie && CKEDITOR.env.version < 10 ) {
 		bender.ignore();
 	}
 
-	var classic = CKEDITOR.replace( 'classic', {
+	CKEDITOR.replace( 'classic', {
 		filebrowserUploadUrl: 'fake-url',
 		filebrowserUploadMethod: 'xhr'
 	} );
diff --git a/tests/plugins/filebrowser/manual/uploadxhrwitherror.md b/tests/plugins/filebrowser/manual/uploadxhrwitherror.md
index 25a26d63591..26ce8a87f71 100644
--- a/tests/plugins/filebrowser/manual/uploadxhrwitherror.md
+++ b/tests/plugins/filebrowser/manual/uploadxhrwitherror.md
@@ -1,16 +1,18 @@
-@bender-tags: 4.8.1, feature, tp3117
+@bender-tags: 4.8.1, feature, 643, tp3117
 @bender-ui: collapsed
 @bender-ckeditor-plugins: wysiwygarea, toolbar, filebrowser, filetools, image, link, flash
 
 ----
 1. Open image dialog
 2. Go to upload tab
-3. Select some image and send it to server
-4. **Alert** should be displayed
-5. Try to upload file again
+3. Select an image and send it to server
 
-Repeat those steps for Link and Flash plugin.
+	**Expected:** An alert with 404 message is displayed.
 
-**Expected:** After first upload attempt, send button is enabled. Which means that every next click trigger new uploading process and generate new alert message.
+5. Click "Send it to the Server" button again
 
-**Unexpected:** After first upload send button is disabled. Second and further upload attempts don't trigger upload process, and alert is not shown.
+	**Expected:** An alert is shown again.
+
+	**Unexpected:** Second and further upload attempts won't trigger upload process, and alert is not shown.
+
+Repeat those steps for Link and Flash plugin.
\ No newline at end of file

From 1886055317ec96d1ef9b257bcbe25ef0625ed8fd Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Wed, 20 Dec 2017 16:40:38 +0100
Subject: [PATCH 16/27] Docs: corrections for config.filebrowserUploadMethod
 API docs.

---
 plugins/filebrowser/plugin.js | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/plugins/filebrowser/plugin.js b/plugins/filebrowser/plugin.js
index 40c68bd44af..41317d6a74f 100644
--- a/plugins/filebrowser/plugin.js
+++ b/plugins/filebrowser/plugin.js
@@ -316,7 +316,6 @@
 								// Append token preventing CSRF attacks.
 								appendToken( fileInput );
 								return true;
-
 							} else {
 								var loader = editor.uploadRepository.create( fileInput.$.files[ 0 ] );
 
@@ -602,24 +601,25 @@
  */
 
 /**
- * Define preferred option to submit file upload with filebrowser plugin. If value is not specified,
- * `'form'` option is used. Additional XHR headers might be set up with {@link CKEDITOR.config#xmlHttpRequestHeaders}.
+ * Defines a preferred option for file uploading in the [File Browser](https://ckeditor.com/cke4/addon/filebrowser) plugin.
  *
  * Available values:
  *
- *	* `'xhr'` - XMLHttpRequest is used to upload file
- *	* `'form'` - Form submit is used to upload file
- *	* `undefiend` - when configuration option is not specified `'form'` configuration is used
+ *	* `'xhr'` - XMLHttpRequest is used to upload file. Using this option allows to set up with Additional XHR headers with
+ * {@link CKEDITOR.config#xmlHttpRequestHeaders} option.
+ *	* `'form'` - (default) File is uploaded by submitting a traditional `<form>` element.
+ *	* `null` - The default method is used.
  *
- * Note: please be aware that `'xhr'` requires {@link CKEDITOR.fileTools} for proper work. Missing this plugins
- * or using browsers which isn't supported {@link CKEDITOR.fileTools#isFileUploadSupported},
- * will force using `'form'` behaviour despite configuration option.
+ * Note: please be aware that `'xhr'` requires the [File Tools](https://ckeditor.com/cke4/addon/filetools) plugin to work
+ * properly. Without the plugin or using a browser that does not support
+ * {@link CKEDITOR.fileTools#isFileUploadSupported file uploading}, will fallback to the `'form'` method despite configuration
+ * option.
  *
- * 	// Modern browsers will use XMLHttpRequest to upload files.
- * 	// IE8 and IE9 will use form submit even tough config option is set to 'xhr'.
- * 	config.filebrowserUploadMethod = 'xhr';
+ *		// Modern browsers will use XMLHttpRequest to upload files.
+ *		// IE8 and IE9 will use form submit even though the config option is set to 'xhr'.
+ *		config.filebrowserUploadMethod = 'xhr';
  *
  * @since 4.8.1
- * @cfg {Boolean} [filebrowserUploadMethod=undefined]
+ * @cfg {String/null} [filebrowserUploadMethod=null]
  * @member CKEDITOR.config
  */

From f299c36d2e8309f0750e71fc8b5ecb5c480b0eac Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Wed, 20 Dec 2017 17:00:39 +0100
Subject: [PATCH 17/27] Docs: adjusted the docs for a config property allowing
 to customize request headers.

---
 plugins/filetools/plugin.js | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/plugins/filetools/plugin.js b/plugins/filetools/plugin.js
index ba4e0254dcc..2735d1b757d 100644
--- a/plugins/filetools/plugin.js
+++ b/plugins/filetools/plugin.js
@@ -913,12 +913,16 @@
  */
 
 /**
- * Additional headers of XMLHttpRequest used during file upload with plugins: {@link CKEDITOR.fileTools} and filebrowser.
+ * Allows to add extra headers for every request made using {@link CKEDITOR.fileTools} API.
  *
- * 	config.xmlHttpRequestHeaders = {
- * 		'Cache-Control': 'no-cache',
- * 		'X-CUSTOM': 'HEADER'
- * 	};
+ * Note that headers can still be customized per a single request, using the
+ * [`fileUploadRequest`](https://docs.ckeditor.com/ckeditor4/docs/#!/api/CKEDITOR.editor-event-fileUploadRequest)
+ * event.
+ *
+ *		config.xmlHttpRequestHeaders = {
+ *			'X-Requested-With': 'XMLHttpRequest',
+ *			'Custom-Header': 'header value'
+ *		};
  *
  * @since 4.8.1
  * @cfg {Object} [xmlHttpRequestHeaders=null]

From ce4afc230e8ceeaa1c584937978f41ffa2181dca Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Wed, 20 Dec 2017 17:05:30 +0100
Subject: [PATCH 18/27] Renamed xmlHttpRequestHeaders config to
 fileTools_requestHeaders.

---
 plugins/filebrowser/plugin.js                   | 2 +-
 plugins/filetools/plugin.js                     | 6 +++---
 tests/plugins/filebrowser/manual/uploadxhr.html | 2 +-
 tests/plugins/filebrowser/uploadbutton.js       | 2 +-
 tests/plugins/filetools/fileloader.js           | 2 +-
 5 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/plugins/filebrowser/plugin.js b/plugins/filebrowser/plugin.js
index 41317d6a74f..69f08f04b4a 100644
--- a/plugins/filebrowser/plugin.js
+++ b/plugins/filebrowser/plugin.js
@@ -606,7 +606,7 @@
  * Available values:
  *
  *	* `'xhr'` - XMLHttpRequest is used to upload file. Using this option allows to set up with Additional XHR headers with
- * {@link CKEDITOR.config#xmlHttpRequestHeaders} option.
+ * {@link CKEDITOR.config#fileTools_requestHeaders} option.
  *	* `'form'` - (default) File is uploaded by submitting a traditional `<form>` element.
  *	* `null` - The default method is used.
  *
diff --git a/plugins/filetools/plugin.js b/plugins/filetools/plugin.js
index 2735d1b757d..b56d19d8eb3 100644
--- a/plugins/filetools/plugin.js
+++ b/plugins/filetools/plugin.js
@@ -49,7 +49,7 @@
 				var fileLoader = evt.data.fileLoader,
 					$formData = new FormData(),
 					requestData = evt.data.requestData,
-					configXHRHeaders = editor.config.xmlHttpRequestHeaders,
+					configXHRHeaders = editor.config.fileTools_requestHeaders,
 					header;
 
 				for ( var name in requestData ) {
@@ -919,12 +919,12 @@
  * [`fileUploadRequest`](https://docs.ckeditor.com/ckeditor4/docs/#!/api/CKEDITOR.editor-event-fileUploadRequest)
  * event.
  *
- *		config.xmlHttpRequestHeaders = {
+ *		config.fileTools_requestHeaders = {
  *			'X-Requested-With': 'XMLHttpRequest',
  *			'Custom-Header': 'header value'
  *		};
  *
  * @since 4.8.1
- * @cfg {Object} [xmlHttpRequestHeaders=null]
+ * @cfg {Object} [fileTools_requestHeaders]
  * @member CKEDITOR.config
  */
diff --git a/tests/plugins/filebrowser/manual/uploadxhr.html b/tests/plugins/filebrowser/manual/uploadxhr.html
index e548952fbc5..ce9bbb8cf43 100644
--- a/tests/plugins/filebrowser/manual/uploadxhr.html
+++ b/tests/plugins/filebrowser/manual/uploadxhr.html
@@ -21,7 +21,7 @@
 	}
 
 	var classic = CKEDITOR.replace( 'classic', {
-		xmlHttpRequestHeaders: {
+		fileTools_requestHeaders: {
 			'hello': 'world',
 			'foo': 'bar'
 		},
diff --git a/tests/plugins/filebrowser/uploadbutton.js b/tests/plugins/filebrowser/uploadbutton.js
index c818a2a80ab..176e2f19aca 100644
--- a/tests/plugins/filebrowser/uploadbutton.js
+++ b/tests/plugins/filebrowser/uploadbutton.js
@@ -29,7 +29,7 @@
 	bender.editors = {
 		xhr: {
 			config: {
-				xmlHttpRequestHeaders: {
+				fileTools_requestHeaders: {
 					foo: 'bar',
 					hello: 'world'
 				},
diff --git a/tests/plugins/filetools/fileloader.js b/tests/plugins/filetools/fileloader.js
index 27468cdb653..06072b7d7a7 100644
--- a/tests/plugins/filetools/fileloader.js
+++ b/tests/plugins/filetools/fileloader.js
@@ -15,7 +15,7 @@
 		listeners = [],
 		editorMock = {
 			config: {
-				xmlHttpRequestHeaders: {
+				fileTools_requestHeaders: {
 					foo: 'bar',
 					hello: 'world'
 				}

From c2c756555654b71eb2fdef71a1543f7e4383a1a5 Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Thu, 21 Dec 2017 10:46:09 +0100
Subject: [PATCH 19/27] Docs: adjusted ticket reference.

---
 plugins/filebrowser/plugin.js | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/plugins/filebrowser/plugin.js b/plugins/filebrowser/plugin.js
index 69f08f04b4a..83f6749050e 100644
--- a/plugins/filebrowser/plugin.js
+++ b/plugins/filebrowser/plugin.js
@@ -310,8 +310,7 @@
 						}
 
 						if ( uploadFile.call( sender, evt ) ) {
-							// Backward compatibility for IE8 and IE9 (https://cksource.tpondemand.com/entity/3117).
-							// With version 4.9.0 change: `!== 'xhr'` to `=== 'form'`.
+							// Use one of two upload strategies, either form or XHR based (#643).
 							if ( editor.config.filebrowserUploadMethod !== 'xhr' || !isFileUploadApiSupported ) {
 								// Append token preventing CSRF attacks.
 								appendToken( fileInput );

From cfd75e8ccf943520c97f19716b737202c41cb925 Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Thu, 21 Dec 2017 11:28:31 +0100
Subject: [PATCH 20/27] Simplified feature detection for file uploading over
 XHR. Minor other refactorings.

---
 plugins/filetools/plugin.js                   | 19 ++++++++-----------
 .../plugins/filebrowser/manual/uploadxhr.html |  2 +-
 .../manual/uploadxhrwitherror.html            |  2 +-
 tests/plugins/filetools/static.js             | 12 ++++++++++++
 4 files changed, 22 insertions(+), 13 deletions(-)
 create mode 100644 tests/plugins/filetools/static.js

diff --git a/plugins/filetools/plugin.js b/plugins/filetools/plugin.js
index b56d19d8eb3..61dd58d965a 100644
--- a/plugins/filetools/plugin.js
+++ b/plugins/filetools/plugin.js
@@ -49,7 +49,7 @@
 				var fileLoader = evt.data.fileLoader,
 					$formData = new FormData(),
 					requestData = evt.data.requestData,
-					configXHRHeaders = editor.config.fileTools_requestHeaders,
+					configXhrHeaders = editor.config.fileTools_requestHeaders,
 					header;
 
 				for ( var name in requestData ) {
@@ -66,9 +66,9 @@
 				// Append token preventing CSRF attacks.
 				$formData.append( 'ckCsrfToken', CKEDITOR.tools.getCsrfToken() );
 
-				if ( configXHRHeaders ) {
-					for ( header in configXHRHeaders ) {
-						fileLoader.xhr.setRequestHeader( header, configXHRHeaders[ header ] );
+				if ( configXhrHeaders ) {
+					for ( header in configXhrHeaders ) {
+						fileLoader.xhr.setRequestHeader( header, configXhrHeaders[ header ] );
 					}
 				}
 
@@ -867,21 +867,18 @@
 		},
 
 		/**
-		 * Property inform if current browser poses native methods used by {@link CKEDITOR.fileTools} to upload files.
+		 * Feature detection indicating whether current browser supports methods essential to send files over XHR request.
 		 *
+		 * @since 4.8.1
 		 * @property {Boolean} isFileUploadSupported
 		 */
 		isFileUploadSupported: ( function() {
-			if ( typeof FileReader === 'function' &&
+			return typeof FileReader === 'function' &&
 				typeof ( new FileReader() ).readAsDataURL === 'function' &&
 				typeof FormData === 'function' &&
 				typeof ( new FormData() ).append === 'function' &&
 				typeof XMLHttpRequest === 'function' &&
-				typeof Blob === 'function' ) {
-
-				return true;
-			}
-			return false;
+				typeof Blob === 'function';
 		} )()
 	} );
 } )();
diff --git a/tests/plugins/filebrowser/manual/uploadxhr.html b/tests/plugins/filebrowser/manual/uploadxhr.html
index ce9bbb8cf43..24c6044aa29 100644
--- a/tests/plugins/filebrowser/manual/uploadxhr.html
+++ b/tests/plugins/filebrowser/manual/uploadxhr.html
@@ -6,7 +6,7 @@
 	var xhr,
 		requests;
 
-	if ( CKEDITOR.env.ie && CKEDITOR.env.version < 10 ) {
+	if ( !CKEDITOR.fileTools.isFileUploadSupported ) {
 		bender.ignore();
 	} else {
 		// Mock XHR
diff --git a/tests/plugins/filebrowser/manual/uploadxhrwitherror.html b/tests/plugins/filebrowser/manual/uploadxhrwitherror.html
index 944862873b7..f5e70e69f14 100644
--- a/tests/plugins/filebrowser/manual/uploadxhrwitherror.html
+++ b/tests/plugins/filebrowser/manual/uploadxhrwitherror.html
@@ -4,7 +4,7 @@
 <div id="output" style="background-color:lightgreen;"></div>
 
 <script>
-	if ( CKEDITOR.env.ie && CKEDITOR.env.version < 10 ) {
+	if ( !CKEDITOR.fileTools.isFileUploadSupported ) {
 		bender.ignore();
 	}
 
diff --git a/tests/plugins/filetools/static.js b/tests/plugins/filetools/static.js
new file mode 100644
index 00000000000..7ca5c75b650
--- /dev/null
+++ b/tests/plugins/filetools/static.js
@@ -0,0 +1,12 @@
+/* bender-tags: editor,clipboard,filetools */
+/* bender-ckeditor-plugins: filetools,clipboard */
+
+( function() {
+	'use strict';
+
+	bender.test( {
+		'test fileTools.isFileUploadSupported': function() {
+			assert.areSame( CKEDITOR.env.ie && CKEDITOR.env.version < 10 ? false : true, CKEDITOR.fileTools.isFileUploadSupported );
+		}
+	} );
+} )();

From 2c7bf7114fa6a50f834eea2b6cc3ee88bceed0d8 Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Thu, 21 Dec 2017 11:42:47 +0100
Subject: [PATCH 21/27] Changelog entry.

---
 CHANGES.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CHANGES.md b/CHANGES.md
index dd1fd39e5c7..cf3c94c3f3a 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -3,6 +3,10 @@
 
 ## CKEditor 4.8.1
 
+New Features:
+
+* [#933](https://github.com/ckeditor/ckeditor-dev/issues/933): [File Browser](https://ckeditor.com/cke4/addon/filetools) plugin can now upload files using XHR requests. This allows for setting custom HTTP headers using [`config.fileTools_requestHeaders`](http://docs.ckeditor.test/#!/api/CKEDITOR.config-cfg-fileTools_requestHeaders) configuration option.
+
 Fixed Issues:
 
 * [#1342](https://github.com/ckeditor/ckeditor-dev/issues/1342): Fixed: [Balloon Toolbar](https://ckeditor.com/cke4/addon/balloontoolbar) should be re-positioned after a [change](https://docs.ckeditor.com/ckeditor4/docs/#!/api/CKEDITOR.editor-event-change) event.

From 4c95176093d1858ffc9f60c3a89cac117e8e86b2 Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Thu, 21 Dec 2017 13:57:31 +0100
Subject: [PATCH 22/27] Tests: corrected file browser xhr upload manual tests.

---
 .../plugins/filebrowser/manual/uploadxhr.html | 31 ++++++++++---------
 .../manual/uploadxhrwitherror.html            | 14 ++++++---
 2 files changed, 25 insertions(+), 20 deletions(-)

diff --git a/tests/plugins/filebrowser/manual/uploadxhr.html b/tests/plugins/filebrowser/manual/uploadxhr.html
index 24c6044aa29..a666342e7b9 100644
--- a/tests/plugins/filebrowser/manual/uploadxhr.html
+++ b/tests/plugins/filebrowser/manual/uploadxhr.html
@@ -3,21 +3,15 @@
 <pre id="output" style="background-color:lightgreen;"></pre>
 
 <script>
-	var xhr,
-		requests;
-
-	if ( !CKEDITOR.fileTools.isFileUploadSupported ) {
-		bender.ignore();
-	} else {
-		// Mock XHR
-		xhr = sinon.useFakeXMLHttpRequest();
+	// Mock XHR
+	var xhr = sinon.useFakeXMLHttpRequest();
 		requests = [];
-		xhr.onCreate = function( xhr ) {
-			requests.push( xhr );
-		};
-		window.onunload = function() {
-			xhr.restore();
-		}
+
+	xhr.onCreate = function( xhr ) {
+		requests.push( xhr );
+	};
+	window.onunload = function() {
+		xhr.restore();
 	}
 
 	var classic = CKEDITOR.replace( 'classic', {
@@ -26,7 +20,14 @@
 			'foo': 'bar'
 		},
 		filebrowserUploadUrl: 'fake-url',
-		filebrowserUploadMethod: 'xhr'
+		filebrowserUploadMethod: 'xhr',
+		on: {
+			instanceReady: function() {
+				if ( !CKEDITOR.fileTools.isFileUploadSupported ) {
+					bender.ignore();
+				}
+			}
+		}
 	} );
 
 	// Display XHR details when CKEDITOR process entire request.
diff --git a/tests/plugins/filebrowser/manual/uploadxhrwitherror.html b/tests/plugins/filebrowser/manual/uploadxhrwitherror.html
index f5e70e69f14..829123af479 100644
--- a/tests/plugins/filebrowser/manual/uploadxhrwitherror.html
+++ b/tests/plugins/filebrowser/manual/uploadxhrwitherror.html
@@ -4,12 +4,16 @@
 <div id="output" style="background-color:lightgreen;"></div>
 
 <script>
-	if ( !CKEDITOR.fileTools.isFileUploadSupported ) {
-		bender.ignore();
-	}
-
 	CKEDITOR.replace( 'classic', {
 		filebrowserUploadUrl: 'fake-url',
-		filebrowserUploadMethod: 'xhr'
+		filebrowserUploadMethod: 'xhr',
+		on: {
+			instanceReady: function() {
+				if ( !CKEDITOR.fileTools.isFileUploadSupported ) {
+					bender.ignore();
+				}
+			}
+		}
 	} );
+
 </script>

From 8276465ac06f48063dbd09dfb3a4caa640af1de0 Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Thu, 21 Dec 2017 18:13:50 +0100
Subject: [PATCH 23/27] Fixed unit tests for Edge, IEs.

---
 tests/plugins/filebrowser/uploadbutton.js | 73 +++++++++++++++--------
 tests/plugins/filetools/fileloader.js     |  2 +-
 2 files changed, 49 insertions(+), 26 deletions(-)

diff --git a/tests/plugins/filebrowser/uploadbutton.js b/tests/plugins/filebrowser/uploadbutton.js
index 176e2f19aca..ab40b55ffd9 100644
--- a/tests/plugins/filebrowser/uploadbutton.js
+++ b/tests/plugins/filebrowser/uploadbutton.js
@@ -4,25 +4,38 @@
 ( function() {
 	'use strict';
 
+	function createFileMock() {
+		window.File = function( data, name ) {
+			var file = new Blob( data , {} );
+			file.name = name;
+
+			return file;
+		};
+	}
+
 	function mockInput( dialog, submit ) {
-		return sinon.stub( dialog, 'getContentElement', function() {
-			return {
-				getInputElement: function() {
-					return {
-						$: {
-							files: [
-								new File( [ '' ], 'sample.png' )
-							],
-							value: 'C:\\fakepath\\sample.gif',
-							form: ( new CKEDITOR.dom.element( 'form' ) ).$
-						}
-					};
-				},
-				getAction: function() {
-					return 'http://url-to-php-form';
-				},
-				submit: submit
-			};
+		return sinon.stub( dialog, 'getContentElement' ).returns( {
+			getInputElement: function() {
+				var ret = {
+					$: {
+						value: 'C:\\fakepath\\sample.gif',
+						form: ( new CKEDITOR.dom.element( 'form' ) ).$
+					}
+				};
+
+				if ( CKEDITOR.fileTools.isFileUploadSupported ) {
+					// Only modern browsers will contain files property.
+					ret.$.files = [
+						new File( [ '' ], 'sample.png' )
+					];
+				}
+
+				return ret;
+			},
+			getAction: function() {
+				return 'http://url-to-php-form';
+			},
+			submit: submit
 		} );
 	}
 
@@ -77,13 +90,10 @@
 	} );
 
 	bender.test( {
-		_should: {
-			ignore: {
-				'test for XHR request': CKEDITOR.env.ie && CKEDITOR.env.version < 9
-			}
-		},
-
 		setUp: function() {
+			if ( typeof MSBlobBuilder === 'function' || !window.File )
+				createFileMock();
+
 			this.xhr = sinon.useFakeXMLHttpRequest();
 			var requests = this.requests = [];
 
@@ -96,7 +106,11 @@
 			this.xhr.restore();
 		},
 
-		'test for xhr request': function() {
+		'test for XHR request': function() {
+			if ( !CKEDITOR.fileTools.isFileUploadSupported ) {
+				assert.ignore();
+			}
+
 			var editor = this.editors.xhr,
 				bot = this.editorBots.xhr;
 
@@ -134,10 +148,15 @@
 				assert.isTrue( mockSubmit.called, 'Submit method should be used.' );
 				inputStub.restore();
 				dialog.hide();
+				assert.isTrue( true );
 			} );
 		},
 
 		'test for xhr loader error': function() {
+			if ( !CKEDITOR.fileTools.isFileUploadSupported ) {
+				assert.ignore();
+			}
+
 			var editor = this.editors.xhr,
 				bot = this.editorBots.xhr;
 
@@ -174,6 +193,10 @@
 		},
 
 		'test for xhr loader abort': function() {
+			if ( !CKEDITOR.fileTools.isFileUploadSupported ) {
+				assert.ignore();
+			}
+
 			var editor = this.editors.xhr,
 				bot = this.editorBots.xhr;
 
diff --git a/tests/plugins/filetools/fileloader.js b/tests/plugins/filetools/fileloader.js
index 06072b7d7a7..2a3be1362d1 100644
--- a/tests/plugins/filetools/fileloader.js
+++ b/tests/plugins/filetools/fileloader.js
@@ -1224,7 +1224,7 @@
 			assert.isTrue( loader.isFinished() );
 		},
 
-		'text custom XHR headers': function() {
+		'test custom XHR headers': function() {
 			var loader = new FileLoader( editorMock, pngBase64 );
 
 			createXMLHttpRequestMock( [ 'load' ] );

From 76cacbef1e1ea15a8d87b51fe1322bf37ca57599 Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Thu, 21 Dec 2017 18:25:53 +0100
Subject: [PATCH 24/27] Extracted common workarounds.

---
 tests/plugins/filebrowser/uploadbutton.js | 14 +++-----------
 tests/plugins/filetools/_helpers/tools.js | 21 +++++++++++++++++++++
 tests/plugins/filetools/fileloader.js     | 18 +++++-------------
 3 files changed, 29 insertions(+), 24 deletions(-)
 create mode 100644 tests/plugins/filetools/_helpers/tools.js

diff --git a/tests/plugins/filebrowser/uploadbutton.js b/tests/plugins/filebrowser/uploadbutton.js
index ab40b55ffd9..bc42d155573 100644
--- a/tests/plugins/filebrowser/uploadbutton.js
+++ b/tests/plugins/filebrowser/uploadbutton.js
@@ -1,18 +1,11 @@
 /* bender-tags: editor */
 /* bender-ckeditor-plugins: dialog,filebrowser,filetools,clipboard */
+/* bender-include: ../filetools/_helpers/tools.js */
+/* global fileTools */
 
 ( function() {
 	'use strict';
 
-	function createFileMock() {
-		window.File = function( data, name ) {
-			var file = new Blob( data , {} );
-			file.name = name;
-
-			return file;
-		};
-	}
-
 	function mockInput( dialog, submit ) {
 		return sinon.stub( dialog, 'getContentElement' ).returns( {
 			getInputElement: function() {
@@ -91,8 +84,7 @@
 
 	bender.test( {
 		setUp: function() {
-			if ( typeof MSBlobBuilder === 'function' || !window.File )
-				createFileMock();
+			fileTools.mockFileType();
 
 			this.xhr = sinon.useFakeXMLHttpRequest();
 			var requests = this.requests = [];
diff --git a/tests/plugins/filetools/_helpers/tools.js b/tests/plugins/filetools/_helpers/tools.js
new file mode 100644
index 00000000000..3a5b5457316
--- /dev/null
+++ b/tests/plugins/filetools/_helpers/tools.js
@@ -0,0 +1,21 @@
+'use strict';
+
+/* exported fileTools */
+
+var fileTools = {
+	// A mockup type that should replace File constructor.
+	fileMock: function( data, name ) {
+		var file = new Blob( data , {} );
+		file.name = name;
+
+		return file;
+	},
+
+	// Replaces window.File constructor with a callable constructor replacement, that
+	// returns file instances mock.
+	mockFileType: function() {
+		if ( typeof MSBlobBuilder === 'function' || !window.File ) {
+			window.File = fileTools.fileMock;
+		}
+	}
+};
\ No newline at end of file
diff --git a/tests/plugins/filetools/fileloader.js b/tests/plugins/filetools/fileloader.js
index 2a3be1362d1..8340eee86ac 100644
--- a/tests/plugins/filetools/fileloader.js
+++ b/tests/plugins/filetools/fileloader.js
@@ -1,9 +1,14 @@
 /* bender-tags: editor,clipboard,filetools */
 /* bender-ckeditor-plugins: filetools */
+/* bender-include: _helpers/tools.js */
+/* global fileTools */
 
 'use strict';
 
 ( function() {
+	// IE/Edge doesn't support File constructor, so there is a need to mimic it.
+	fileTools.mockFileType();
+
 	var File = window.File,
 		Blob = window.Blob,
 		FormData = window.FormData,
@@ -27,15 +32,6 @@
 			}
 		};
 
-	function createFileMock() {
-		window.File = File = function( data, name ) {
-			var file = new Blob( data , {} );
-			file.name = name;
-
-			return file;
-		};
-	}
-
 	function createFormDataMock() {
 		window.FormData = function() {
 			var entries = {},
@@ -243,10 +239,6 @@
 				assert.ignore();
 			}
 
-			// IE doesn't support File constructor, so there is a need to mimic it.
-			if ( typeof MSBlobBuilder === 'function' )
-				createFileMock();
-
 			// FormData in IE & Chrome 47- supports only adding data, not getting it, so mocking (polyfilling?) is required.
 			// Note that mocking is needed only for tests, as CKEditor.fileTools uses only append method
 			if ( !FormData.prototype.get || !FormData.prototype.has )

From 1eeab6fbc161f615f8467be8072f7aea9e703522 Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Fri, 22 Dec 2017 12:45:42 +0100
Subject: [PATCH 25/27] Tests: removed dummy assertion.

---
 tests/plugins/filebrowser/uploadbutton.js | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tests/plugins/filebrowser/uploadbutton.js b/tests/plugins/filebrowser/uploadbutton.js
index bc42d155573..d05f12b8078 100644
--- a/tests/plugins/filebrowser/uploadbutton.js
+++ b/tests/plugins/filebrowser/uploadbutton.js
@@ -140,7 +140,6 @@
 				assert.isTrue( mockSubmit.called, 'Submit method should be used.' );
 				inputStub.restore();
 				dialog.hide();
-				assert.isTrue( true );
 			} );
 		},
 

From 5a577feb3317283a0366753c521aa697d11d0435 Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Fri, 22 Dec 2017 14:36:57 +0100
Subject: [PATCH 26/27] Tests: corrected language config property.

---
 tests/plugins/filebrowser/uploadbutton.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/plugins/filebrowser/uploadbutton.js b/tests/plugins/filebrowser/uploadbutton.js
index d05f12b8078..de6fbe00262 100644
--- a/tests/plugins/filebrowser/uploadbutton.js
+++ b/tests/plugins/filebrowser/uploadbutton.js
@@ -41,7 +41,7 @@
 				},
 				filebrowserUploadUrl: 'foo',
 				filebrowserUploadMethod: 'xhr',
-				lang: 'en'
+				language: 'en'
 			}
 		},
 		submit: {

From cd36fe81794bd499dba534b75e675077e1af43ce Mon Sep 17 00:00:00 2001
From: Marek Lewandowski <m.lewandowski@cksource.com>
Date: Fri, 22 Dec 2017 15:01:20 +0100
Subject: [PATCH 27/27] Tests: corrected manual test expected result.

---
 tests/plugins/filebrowser/manual/uploadxhr.md | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/tests/plugins/filebrowser/manual/uploadxhr.md b/tests/plugins/filebrowser/manual/uploadxhr.md
index 17ba12f107a..54a4b8410cf 100644
--- a/tests/plugins/filebrowser/manual/uploadxhr.md
+++ b/tests/plugins/filebrowser/manual/uploadxhr.md
@@ -8,8 +8,14 @@
 3. Select some image and send it to server
 4. Close dialog (There might appear warning that image url is not set up)
 
-**Expected:** Below editor will appear green div with listed headers attempted to send. There are 2 headers in single line:
-`hello: world, foo: bar`.
+**Expected:** Below editor will appear green div with listed headers attempted to send. You should see following headers for each case:
+
+```
+{
+    "hello": "world",
+    "foo": "bar"
+}
+```
 
 **Unexpected:** Headers are not listed below.