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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');
});
}
})();

@derickr derickr Sep 15, 2026

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I don't understand why there is a closure here that you then need to execute immediately, nor why the header_register is there, considering that literally the next line in the code also sets a header.

@svpernova09 svpernova09 Sep 15, 2026

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It was an attempt at encapsulation, and I went a bit overboard.

We shouldn't need this change if Bunny resolves the issue on their side. According to the support ticket, they've escalated it on their side, so this PR can wait until we see the outcome before moving forward.


// 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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