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HTML API: Double escape character refs when setting attribute values #10143

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sirreal wants to merge 13 commits into from
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HTML API: Double escape character refs when setting attribute values #10143

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8d8622e
Layout ternary on multiple lines
sirreal Oct 3, 2025
8e0d406
Escape with htmlspecialchars
sirreal Oct 3, 2025
66af901
Add test
sirreal Oct 3, 2025
ff62be1
Use assertEqualHTML for legible test output
sirreal Oct 3, 2025
daef88f
Update two tests for no-double-encode behavior
sirreal Oct 3, 2025
c2e2ad4
Update tests
sirreal Oct 3, 2025
5e5473a
Update block supports tests
sirreal Oct 3, 2025
40cfce5
Merge branch 'trunk' into trac-64054
sirreal Oct 8, 2025
1435b6e
Update escaping function to use simple strtr()
sirreal Oct 8, 2025
b581113
Update comment about attribute value escaping
sirreal Oct 8, 2025
0db1374
Improve function description following review suggestion.
sirreal Oct 9, 2025
605b00d
Fix typo in comment, expand examples, and copy to HTML Processor.
dmsnell Oct 9, 2025
00f01bf
Moar text fixes
dmsnell Oct 9, 2025
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Update escaping function to use simple strtr()
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@sirreal
sirreal committed Oct 8, 2025
commit 1435b6e1dbd24fdfa28b0992ef12b53ddeb930e9
22 changes: 20 additions & 2 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 @@ -3757,7 +3757,16 @@ public function set_modifiable_text( string $plaintext_content ): bool {
$this->lexical_updates['modifiable text'] = new WP_HTML_Text_Replacement(
$this->text_starts_at,
$this->text_length,
htmlspecialchars( $plaintext_content, ENT_QUOTES | ENT_HTML5 )
strtr(
$plaintext_content,
array(
'<' => '&lt;',
'>' => '&gt;',
'&' => '&amp;',
'"' => '&quot;',
"'" => '&apos;',
)
)
);

return true;
Expand Down Expand Up @@ -3957,7 +3966,16 @@ public function set_attribute( $name, $value ): bool {
*/
$escaped_new_value = in_array( $comparable_name, wp_kses_uri_attributes(), true )
? esc_url( $value )
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@westonruter westonruter Oct 6, 2025 •
edited
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The esc_url() function also does some stuff with entities, namely:

wordpress-develop/src/wp-includes/formatting.php

Lines 4522 to 4527 in fe2b33f

// Replace ampersands and single quotes only when displaying.
if ( 'display' === $_context ) {
$url = wp_kses_normalize_entities( $url );
$url = str_replace( '&amp;', '&#038;', $url );
$url = str_replace( "'", '&#039;', $url );
}

To avoid that, I think using esc_url_raw() is preferable:

Suggested change
? esc_url( $value )
? htmlspecialchars( esc_url_raw( $value ) )

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@sirreal sirreal Oct 8, 2025

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This line is only a formatting change, I broke the ternary onto three lines.

Can we consider that suggestion in a separate ticket and PR?

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@westonruter westonruter Oct 9, 2025 •
edited
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Ah sure, but it it is related to the double-escaping issue, because esc_url() does wp_kses_normalize_entities() which includes converting all & to &amp; among other things. For example, these:

var_dump( esc_url( 'http://example.com/?foo&amp;bar' ) );
var_dump( esc_url( 'http://example.com/?foo&#038;bar' ) );
var_dump( esc_url( 'http://example.com/?foo&bar' ) );

All result in:

string(32) "http://example.com/?foo&#038;bar"
string(32) "http://example.com/?foo&#038;bar"
string(32) "http://example.com/?foo&#038;bar"

I don't really see why a URI attribute should be treated differently at the HTML API layer. So this could instead just be:

$escaped_new_value = strtr(
	$value,
	array(
		'<' => '&lt;',
		'>' => '&gt;',
		'&' => '&amp;',
		'"' => '&quot;',
		"'" => '&apos;',
	)
);

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@sirreal sirreal Oct 9, 2025

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You're absolutely right that the double-escaping issue also exists in esc_url(), that's unfortunate. esc_url() does a lot of things, it doesn't seem as easily replaced as esc_attr() or esc_html(). I suspect more discussion will be necessary regarding URL-related changes which is why I'm reluctant to include those changes here.

See r58472 and r58473.

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@westonruter westonruter Oct 9, 2025

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OK, sounds good.

: htmlspecialchars( $value, ENT_QUOTES | ENT_HTML5 );
: strtr(
$value,
array(
'<' => '&lt;',
'>' => '&gt;',
'&' => '&amp;',
'"' => '&quot;',
"'" => '&apos;',
)
);

// If the escaping functions wiped out the update, reject it and indicate it was rejected.
if ( '' === $escaped_new_value && '' !== $value ) {
Expand Down
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