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Set Cache-Control to no-store on paths containing %2F/%5C/%2E #2018

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Set Cache-Control to no-store on paths containing %2F/%5C/%2E #2018

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13 changes: 13 additions & 0 deletions include/prepend.inc
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,19 @@ require_once __DIR__ . '/../src/autoload.php';
// See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9
// for cache control header descriptions (used in many places on the site).

// Our CDN decodes %2F/%5C/%2E and resolves dot segments to build its cache key,
// but forwards the raw path to us, so a response for such a path can be stored
// under a different URL (www.php.net "/" was poisoned this way in 2026-09).
// Keep serving these requests, but never let the response be cached.
(function (): void {
$path = explode('?', $_SERVER['REQUEST_URI'] ?? '/', 2)[0];
if (preg_match('~%(?:2f|5c|2e)|\\\\|(?:^|/)\.{1,2}(?:/|$)~i', $path)) {
header_register_callback(static function (): void {
header('Cache-Control: no-store');
});
}
})();

// Provide default content-type, charset and language information
// Manual pages will override this, and maybe others too
header("Content-language: en");
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