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Security: Harden HTML event attribute filtering - refs GHSA-9wff-vv7j-p3cc #9243

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Merged
christianbeeznest merged 1 commit into from
Oct 16, 2026
+9 −3
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Security: Harden HTML event attribute filtering - refs GHSA-9wff-vv7j-p3cc #9243

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12 changes: 9 additions & 3 deletions src/Chamilo/CoreBundle/Component/HTMLPurifier/Filter/RemoveOnAttributes.php
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Original file line number Diff line number Diff line change
Expand Up @@ -17,10 +17,16 @@ public function preFilter($html, $config, $context)

public static function filter($html)
{
// Strip null bytes before regex matching to prevent bypass via on\x00load patterns
// Strip null bytes before regex matching to prevent bypass via on\x00load patterns.
$html = str_replace("\0", '', $html);
$pattern = '/\s+on\w+\s*=\s*(?:"[^"]*"|\'[^\']*\'|[^\s>]+)/i';
$pattern = '/(?:=\s*(?:"[^"]*"|\'[^\']*\'|[^\s>]+))(*SKIP)(*F)|(?:\s+|\/+|(?<=["\']))on\w+\s*=\s*(?:"[^"]*"|\'[^\']*\'|[^\s>]+)/i';

return preg_replace($pattern, '', $html);
return preg_replace_callback(
'/<(?:[^>"\']+|"[^"]*"|\'[^\']*\')*>/s',
function ($matches) use ($pattern) {
return preg_replace($pattern, '', $matches[0]);
},
$html
);
}
}
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