From 9948692ecd6cc9bb25353e519a75041adc2350d7 Mon Sep 17 00:00:00 2001
From: Carlo Goetz <carlo.goetz@inovex.de>
Date: Thu, 30 Oct 2025 09:20:52 +0100
Subject: [PATCH] fix: [#1947] Decode &apos; / numeric character references in
 attr values

- attribute values can contain named and numeric character references
  per https://html.spec.whatwg.org/multipage/syntax.html#syntax-attribute-value
- add decoding for all numeric character references
- add decoding for &apos;, this could probably appear in single-quoted
  attribute values
- ignore other named character references, the list is huge
---
 .../happy-dom/src/utilities/XMLEncodeUtility.ts   |  7 ++++++-
 .../happy-dom/test/html-parser/HTMLParser.test.ts | 15 +++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/packages/happy-dom/src/utilities/XMLEncodeUtility.ts b/packages/happy-dom/src/utilities/XMLEncodeUtility.ts
index 8aef0b063..a268d7ba4 100644
--- a/packages/happy-dom/src/utilities/XMLEncodeUtility.ts
+++ b/packages/happy-dom/src/utilities/XMLEncodeUtility.ts
@@ -67,7 +67,12 @@ export default class XMLEncodeUtility {
 			return '';
 		}
 
-		return value.replace(/&quot;/gu, '"').replace(/&amp;/gu, '&');
+		return value
+			.replace(/&quot;/gu, '"')
+			.replace(/&amp;/gu, '&')
+			.replace(/&apos;/gu, "'")
+			.replace(/&#(\d+);/gu, (_match, dec) => String.fromCharCode(parseInt(dec, 10)))
+			.replace(/&#x([A-Fa-f\d]+);/gu, (_match, hex) => String.fromCharCode(parseInt(hex, 16)));
 	}
 
 	/**
diff --git a/packages/happy-dom/test/html-parser/HTMLParser.test.ts b/packages/happy-dom/test/html-parser/HTMLParser.test.ts
index d7f9b2394..ef15bc2a3 100644
--- a/packages/happy-dom/test/html-parser/HTMLParser.test.ts
+++ b/packages/happy-dom/test/html-parser/HTMLParser.test.ts
@@ -2208,5 +2208,20 @@ describe('HTMLParser', () => {
                 </tr>
             `);
 		});
+
+		it('Handles numeric character references and &apos; in attribute values for #1947', () => {
+			const result = new HTMLParser(window).parse(`
+                <div>
+                    <span data-foo="&#34;"></span>
+                    <span data-foo="&#x22;"></span>
+                    <span data-foo="&apos;"></span>
+                </div>`);
+			expect(new HTMLSerializer().serializeToString(result)).toBe(`
+                <div>
+                    <span data-foo="&quot;"></span>
+                    <span data-foo="&quot;"></span>
+                    <span data-foo="'"></span>
+                </div>`);
+		});
 	});
 });