diff --git a/routes/submit/index.tsx b/routes/submit/index.tsx
index 43f960f2c967..e35656d5192e 100644
--- a/routes/submit/index.tsx
+++ b/routes/submit/index.tsx
@@ -12,6 +12,7 @@ import Head from "@/components/Head.tsx";
 import IconCheckCircle from "tabler_icons_tsx/circle-check.tsx";
 import IconCircleX from "tabler_icons_tsx/circle-x.tsx";
 import { SignedInState } from "@/utils/middleware.ts";
+import { isPublicUrl, isValidUrl } from "@/utils/url_validation.ts";
 
 export const handler: Handlers<SignedInState, SignedInState> = {
   async POST(req, ctx) {
@@ -24,8 +25,9 @@ export const handler: Handlers<SignedInState, SignedInState> = {
     }
 
     try {
-      // Throws if an invalid URL
-      new URL(url);
+      if (!isValidUrl(url) || !isPublicUrl(url)) {
+        return new Response(null, { status: 400 });
+      }
     } catch {
       return new Response(null, { status: 400 });
     }
diff --git a/utils/url_validation.ts b/utils/url_validation.ts
new file mode 100644
index 000000000000..519cb4e345e5
--- /dev/null
+++ b/utils/url_validation.ts
@@ -0,0 +1,29 @@
+// Copyright 2023 the Deno authors. All rights reserved. MIT license.
+
+export function isValidUrl(string: string): boolean {
+  try {
+    const { protocol } = new URL(string);
+    return protocol.startsWith("http");
+  } catch {
+    return false;
+  }
+}
+
+export function isPublicUrl(string: string): boolean {
+  try {
+    const { hostname } = new URL(string);
+    const ranges = [
+      /^localhost$/,
+      /^127\.\d{1,3}\.\d{1,3}\.\d{1,3}$/,
+      /^::1$/,
+      /^0:0:0:0:0:0:0:1$/,
+      /^10\.\d{1,3}\.\d{1,3}\.\d{1,3}$/,
+      /^172\.(1[6-9]|2\d|3[0-1])\.\d{1,3}\.\d{1,3}$/,
+      /^192\.168\.\d{1,3}\.\d{1,3}$/,
+    ];
+
+    return !ranges.some((range) => range.test(hostname));
+  } catch (_) {
+    return false;
+  }
+}
diff --git a/utils/url_validation_test.ts b/utils/url_validation_test.ts
new file mode 100644
index 000000000000..c10597cf3912
--- /dev/null
+++ b/utils/url_validation_test.ts
@@ -0,0 +1,24 @@
+// Copyright 2023 the Deno authors. All rights reserved. MIT license.
+
+import { assertEquals } from "std/testing/asserts.ts";
+import { isPublicUrl, isValidUrl } from "./url_validation.ts";
+
+Deno.test("[url_validation] isValidUrl()", () => {
+  assertEquals(isValidUrl("https://hunt.deno.land/"), true);
+  assertEquals(isValidUrl("http://hunt.deno.land/"), true);
+  assertEquals(isValidUrl("ws://hunt.deno.land/"), false);
+  assertEquals(isValidUrl("wss://hunt.deno.land/"), false);
+  assertEquals(isValidUrl("invalidurl"), false);
+});
+
+Deno.test("[url_validation] isPublicUrl()", () => {
+  assertEquals(isPublicUrl("https://hunt.deno.land/"), true);
+  assertEquals(isPublicUrl("http://hunt.deno.land/"), true);
+  assertEquals(isPublicUrl("ws://hunt.deno.land/"), true);
+  assertEquals(isPublicUrl("http://localhost/"), false);
+  assertEquals(isPublicUrl("http://127.0.0.1/"), false);
+  assertEquals(isPublicUrl("http://::1/"), false);
+  assertEquals(isPublicUrl("http://10.0.0.0/"), false);
+  assertEquals(isPublicUrl("http://172.16.0.0/"), false);
+  assertEquals(isPublicUrl("http://192.168.0.0/"), false);
+});