From 3c2c7ce1e270561dc49831c8157e17c3a62ca14a Mon Sep 17 00:00:00 2001
From: Moonchild <moonchild@palemoon.org>
Date: Thu, 19 Jun 2025 12:55:54 +0200
Subject: [PATCH] No issue - Escape `<` and `>` in element attribute values.

Per spec, extend escaping of attribute value characters to include
`<` and `>`. We already did this for text fragments, and it makes sense
to apply the same to attribute values. We are at parity with mainstream
that default-escape attribute values this way in current releases.
---
 dom/base/nsContentUtils.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index ab7eb59774..fb4eee8f0e 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -9359,6 +9359,12 @@ private:
       case 0x00A0:
         aOut.AppendLiteral("&nbsp;");
         break;
+      case '<':
+        aOut.AppendLiteral("&lt;");
+        break;
+      case '>':
+        aOut.AppendLiteral("&gt;");
+        break;
       default:
         aOut.Append(*c);
         break;
@@ -9500,6 +9506,12 @@ AppendEncodedAttributeValue(nsAutoString* aValue, StringBuilder& aBuilder)
       case 0x00A0:
         extraSpaceNeeded += ArrayLength("&nbsp;") - 2;
         break;
+      case '<':
+        extraSpaceNeeded += ArrayLength("&lt;") - 2;
+        break;
+      case '>':
+        extraSpaceNeeded += ArrayLength("&gt;") - 2;
+        break;
       default:
         break;
     }