From 3ec32b87d4145faa07e17904bae169e03d819366 Mon Sep 17 00:00:00 2001
From: Andrew Serong <14988353+andrewserong@users.noreply.github.com>
Date: Fri, 14 Oct 2022 14:55:35 +1100
Subject: [PATCH] Update 6.1 CSS filter to match core

---
 lib/compat/wordpress-6.1/blocks.php | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/lib/compat/wordpress-6.1/blocks.php b/lib/compat/wordpress-6.1/blocks.php
index b22fb1fe18aee8..cd61b70a07f09b 100644
--- a/lib/compat/wordpress-6.1/blocks.php
+++ b/lib/compat/wordpress-6.1/blocks.php
@@ -38,11 +38,15 @@ function gutenberg_safe_style_attrs_6_1( $attrs ) {
  */
 function gutenberg_safecss_filter_attr_allow_css_6_1( $allow_css, $css_test_string ) {
 	if ( false === $allow_css ) {
-		// Allow some CSS functions.
-		$css_test_string = preg_replace( '/\b(?:calc|min|max|minmax|clamp)\(((?:\([^()]*\)?|[^()])*)\)/', '', $css_test_string );
-
-		// Allow CSS var.
-		$css_test_string = preg_replace( '/\(?var\(--[\w\-\()[\]\,\s]*\)/', '', $css_test_string );
+		/*
+		 * Allow CSS functions like var(), calc(), etc. by removing them from the test string.
+		 * Nested functions and parentheses are also removed, so long as the parentheses are balanced.
+		 */
+		$css_test_string = preg_replace(
+			'/\b(?:var|calc|min|max|minmax|clamp)(\((?:[^()]|(?1))*\))/',
+			'',
+			$css_test_string
+		);
 
 		// Check for any CSS containing \ ( & } = or comments,
 		// except for url(), calc(), or var() usage checked above.