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HTML API: Ensure correct encoding of modified class names #10591

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HTML API: Ensure correct encoding of modified class names #10591

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2c8756b
Add failing test for ticket 64340
sirreal Dec 3, 2025
cf42da8
Include correctly encoded HTML class name "&" initially
sirreal Dec 3, 2025
135f3dd
Add missing attribute decode when accessing raw class attribute HTML
sirreal Dec 3, 2025
99d7043
Update tests enforcing double-encoding
sirreal Dec 3, 2025
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10 changes: 6 additions & 4 deletions src/wp-includes/html-api/class-wp-html-tag-processor.php
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Original file line number Diff line number Diff line change
Expand Up @@ -2342,10 +2342,12 @@ private function class_name_updates_to_attributes_updates(): void {
}

if ( false === $existing_class && isset( $this->attributes['class'] ) ) {
$existing_class = substr(
$this->html,
$this->attributes['class']->value_starts_at,
$this->attributes['class']->value_length
$existing_class = WP_HTML_Decoder::decode_attribute(
substr(
$this->html,
$this->attributes['class']->value_starts_at,
$this->attributes['class']->value_length
)
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@dmsnell dmsnell Dec 3, 2025

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I’ve been staring at this for a bit now and have no idea how we missed it. Surely we didn’t overlook this since 6.2 in the original introduction?

but you know what? we did!

php > $p = new WP_HTML_Tag_Processor( '<div class="&amp; &#x61;bc">' );
php > $p->next_tag();
php > $p->add_class( '&' );
php > $p->add_class( 'abc' );
php > echo $p->get_updated_html();
<div class="&amp; &#x61;bc &amp; abc">
php > $p->remove_class( 'abc' );
php > echo $p->get_updated_html();
<div class="&amp; &#x61;bc &amp;">
php > $p->remove_class( '&' );
php > echo $p->get_updated_html();
<div class="&amp; &#x61;bc &amp;">

now I don’t remember why; maybe it was performance-related or maybe it was a choice to lean on already-existing bugs, but I suppose it’s proper here to fix it regardless.

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@sirreal sirreal Dec 3, 2025

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Yes, there's been a latent issue for a while that was covered up by the behavior of esc_html(). It's become very clear with the change in 6.9 to use more rigorous attribute encoding.

);
}

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48 changes: 46 additions & 2 deletions tests/phpunit/tests/html-api/wpHtmlTagProcessor.php
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Expand Up @@ -2887,11 +2887,11 @@ public static function data_updating_attributes_in_malformed_html() {
),
'HTML tag opening inside attribute value' => array(
'input' => '<pre id="<code" class="wp-block-code <code is poetry&gt;"><code>This &lt;is> a &lt;strong is="true">thing.</code></pre><span>test</span>',
'expected' => '<pre foo="bar" id="<code" class="wp-block-code &lt;code is poetry&amp;gt; firstTag"><code class="secondTag">This &lt;is> a &lt;strong is="true">thing.</code></pre><span>test</span>',
'expected' => '<pre foo="bar" id="<code" class="wp-block-code &lt;code is poetry&gt; firstTag"><code class="secondTag">This &lt;is> a &lt;strong is="true">thing.</code></pre><span>test</span>',
),
'HTML tag brackets in attribute values and data markup' => array(
'input' => '<pre id="<code-&gt;-block-&gt;" class="wp-block-code <code is poetry&gt;"><code>This &lt;is> a &lt;strong is="true">thing.</code></pre><span>test</span>',
'expected' => '<pre foo="bar" id="<code-&gt;-block-&gt;" class="wp-block-code &lt;code is poetry&amp;gt; firstTag"><code class="secondTag">This &lt;is> a &lt;strong is="true">thing.</code></pre><span>test</span>',
'expected' => '<pre foo="bar" id="<code-&gt;-block-&gt;" class="wp-block-code &lt;code is poetry&gt; firstTag"><code class="secondTag">This &lt;is> a &lt;strong is="true">thing.</code></pre><span>test</span>',
Comment on lines +2890 to +2894
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@sirreal sirreal Dec 3, 2025 •
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These tests seem to have been ensuring incorrect behavior.

In both cases updated here an input class like poetry&gt; (decoded value poetry>) was changed to poetry&amp;gt; (decoded value poetry&gt;).

They were updated in #10143. This change restores their original (correct) assertion.

),
'Single and double quotes in attribute value' => array(
'input' => '<p title="Demonstrating how to use single quote (\') and double quote (&quot;)"><span>test</span>',
Expand Down Expand Up @@ -3028,6 +3028,50 @@ public static function data_updating_attributes_in_malformed_html() {
);
}

/**
* @ticket 64340
*/
public function test_class_changes_produce_correct_html() {
$processor = new WP_HTML_Tag_Processor( '<div class="&amp;">' );
$processor->next_tag();

$processor->add_class( '"' );
$processor->get_updated_html();

$processor->add_class( 'OK' );
$processor->get_updated_html();

$this->assertTrue( $processor->has_class( '&' ), 'Missing expected "&" class.' );
$this->assertTrue( $processor->has_class( '"' ), 'Missing expected \'"\' class.' );
$this->assertTrue( $processor->has_class( 'OK' ), 'Missing expected "OK" class.' );

$expected = '<div class="&amp; &quot; OK">';
$this->assertEqualHTML(
$expected,
$processor->get_updated_html(),
'<body>',
'HTML was not correctly updated after adding classes.'
);

$processor->remove_class( '&' );
$processor->get_updated_html();

$processor->remove_class( '"' );
$processor->get_updated_html();

$this->assertFalse( $processor->has_class( '&' ) );
$this->assertFalse( $processor->has_class( '"' ) );
$this->assertTrue( $processor->has_class( 'OK' ) );

$expected = '<div class="OK">';
$this->assertEqualHTML(
$expected,
$processor->get_updated_html(),
'<body>',
'HTML was not correctly updated after removing classes.'
);
}

/**
* @covers WP_HTML_Tag_Processor::next_tag
*/
Expand Down
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