CVE-2026-55891

## Vulnerability Details A reflected JSON injection allows an attacker to return arbitrary data in the JSON endpoints (like ` /?jsonld=` and `/?pasteid`). ### Root Cause `Request::getRequestUri()` sanitizes `$_SERVER['REQUEST_URI']` with `FILTER_SANITIZE_URL`: ```php public function getRequestUri() { $uri = array_key_exists('REQUEST_URI', $_SERVER) ? filter_var($_SERVER['REQUEST_URI'], FILTER_SANITIZE_URL) : ''; return empty($uri) ? '/' : $uri; } ``` `FILTER_SANITIZE_URL` does **not** strip `"`, `'`, `<`, `>` characters (per the PHP manual's allowed-character list for this filter). So the raw, attacker-controlled request URI (including query string) passes through almost unmodified into `Controller::$_urlBase` (set in `_init()`). In `Controller::_jsonld()`, `$_urlBase` is spliced directly into one of the static `.jsonld` templates (`js/types.jsonld`, `js/paste.jsonld`, etc.) with a plain `str_replace()`, without any JSON-escaping: ```php $content = str_replace( '?jsonld=', $this->_urlBase . '?jsonld=', file_get_contents($file) ); ... header('Content-type: application/ld+json'); header('Access-Control-Allow-Origin: *'); header('Access-Control-Allow-Methods: GET'); echo $content; ``` A request URI containing a literal `"` therefore breaks out of the JSON string in the `"@context"."pb"` value and injects arbitrary attacker-controlled key/value pairs into the response body, which is served with `Content-Type: application/ld+json` and `Access-Control-Allow-Origin: *`. Additionally, the `jsonld` case in `Controller::__construct()` returns early: ```php case 'jsonld': $this->_jsonld($this->_request->getParam('jsonld')); return; ``` This bypasses `_setCacheHeaders()` and all of the security headers normally applied in `_view()` (notably `X-Content-Type-Options: nosniff`, CSP, `X-Frame-Options`, `Referrer-Policy`). So this is the only response path lacking `X-Content-Type-Options: nosniff`. ### Attack Scenario 1. An attacker crafts a r