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<dt style="float: left; width: 6em; font-weight: bold">Revision</dt> <dd><a style="font-weight: bold" href="https://core.trac.wordpress.org/changeset/58845">58845</a><script type="application/ld+json">{"@context":"http://schema.org","@type":"EmailMessage","description":"Review this Commit","action":{"@type":"ViewAction","url":"https://core.trac.wordpress.org/changeset/58845","name":"Review Commit"}}</script></dd>
<dt style="float: left; width: 6em; font-weight: bold">Author</dt> <dd>dmsnell</dd>
<dt style="float: left; width: 6em; font-weight: bold">Date</dt> <dd>2024-08-02 23:46:45 +0000 (Fri, 02 Aug 2024)</dd>
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<pre style='padding-left: 1em; margin: 2em 0; border-left: 2px solid #ccc; line-height: 1.25; font-size: 105%; font-family: sans-serif'>HTML API: Fix an infinite loop in certain unclosed SCRIPT tags.

When the Tag Processor (or HTML Processor) attempts to parse certain
incomplete script tags, the parser enters an infinite loop and will
hang indefinitely. The conditions to reach this situation are:

- Input HTML ends with an open script tag.
- The final character of input is `-` or `<`.

The infinite loop was caused by the parser-advancing increment not being
called when two `||` OR conditions short-circuited. If the first
condition was true, the `$at++` code was never reached.

This path resolves the issue.

Developed in https://github.com/wordpress/wordpress-develop/pull/7128
Discussed in https://core.trac.wordpress.org/ticket/61810

Follow-up to <a href="https://core.trac.wordpress.org/changeset/55203">[55203]</a>.

Props: dmsnell, jonsurrell.
Fixes <a href="https://core.trac.wordpress.org/ticket/61810">#61810</a>.</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunksrcwpincludeshtmlapiclasswphtmltagprocessorphp">trunk/src/wp-includes/html-api/class-wp-html-tag-processor.php</a></li>
<li><a href="#trunktestsphpunittestshtmlapiwpHtmlTagProcessorphp">trunk/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunksrcwpincludeshtmlapiclasswphtmltagprocessorphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-includes/html-api/class-wp-html-tag-processor.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-includes/html-api/class-wp-html-tag-processor.php    2024-08-02 22:57:46 UTC (rev 58844)
+++ trunk/src/wp-includes/html-api/class-wp-html-tag-processor.php      2024-08-02 23:46:45 UTC (rev 58845)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1431,8 +1431,15 @@
</span><span class="cx" style="display: block; padding: 0 10px">                                continue;
</span><span class="cx" style="display: block; padding: 0 10px">                        }
</span><span class="cx" style="display: block; padding: 0 10px"> 
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                        // Everything of interest past here starts with "<".
-                       if ( $at + 1 >= $doc_length || '<' !== $html[ $at++ ] ) {
</del><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+                 if ( $at + 1 >= $doc_length ) {
+                               return false;
+                       }
+
+                       /*
+                        * Everything of interest past here starts with "<".
+                        * Check this character and advance position regardless.
+                        */
+                       if ( '<' !== $html[ $at++ ] ) {
</ins><span class="cx" style="display: block; padding: 0 10px">                                 continue;
</span><span class="cx" style="display: block; padding: 0 10px">                        }
</span><span class="cx" style="display: block; padding: 0 10px"> 
</span></span></pre></div>
<a id="trunktestsphpunittestshtmlapiwpHtmlTagProcessorphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php 2024-08-02 22:57:46 UTC (rev 58844)
+++ trunk/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php   2024-08-02 23:46:45 UTC (rev 58845)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -2875,4 +2875,32 @@
</span><span class="cx" style="display: block; padding: 0 10px">                        'Should have properly applied the update from in front of the cursor.'
</span><span class="cx" style="display: block; padding: 0 10px">                );
</span><span class="cx" style="display: block; padding: 0 10px">        }
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+
+       /**
+        * Test an infinite loop bugfix in incomplete script tag parsing.
+        *
+        * @small
+        *
+        * @ticket 61810
+        */
+       public function test_script_tag_processing_no_infinite_loop_final_dash() {
+               $processor = new WP_HTML_Tag_Processor( '<script>-' );
+
+               $this->assertFalse( $processor->next_tag() );
+               $this->assertTrue( $processor->paused_at_incomplete_token() );
+       }
+
+       /**
+        * Test an infinite loop bugfix in incomplete script tag parsing.
+        *
+        * @small
+        *
+        * @ticket 61810
+        */
+       public function test_script_tag_processing_no_infinite_loop_final_left_angle_bracket() {
+               $processor = new WP_HTML_Tag_Processor( '<script><' );
+
+               $this->assertFalse( $processor->next_tag() );
+               $this->assertTrue( $processor->paused_at_incomplete_token() );
+       }
</ins><span class="cx" style="display: block; padding: 0 10px"> }
</span></span></pre>
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