Texturize: Transform & into & in tag attributes.

[35709] was overly broad, and stopped transforming `&` characters within tag attributes. So that sites aren't generating invalid HTML, we need to restore this functionality, while continuing to not transform `&` within blocked tags.

Fixes #35008 for trunk.



git-svn-id: https://develop.svn.wordpress.org/trunk@36036 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/formatting.php

@@ -233,6 +233,10 @@ function wptexturize( $text, $reset = false ) {
 				continue;
 			} else {
 				// This is an HTML element delimiter.
+
+				// Replace each & with & unless it already looks like an entity.
+				$curl = preg_replace( '/&(?!#(?:\d+|x[a-f0-9]+);|[a-z1-4]{1,8};)/i', '&', $curl );
+
 				_wptexturize_pushpop_element( $curl, $no_texturize_tags_stack, $no_texturize_tags );
 			}