Medium · published December 22, 2022
Cross-Site Tracing occurs when a server will echo a request back via the Trace method, allowing an XSS attack to access to authorization headers and cookies inaccessible to JavaScript (such as cookies protected by HTTPOnly). To mitigate this attack, browsers placed limits on <code>fetch()</code> and XMLHttpRequest; however some webservers have implemented non-standard headers such as <code>X-Http-Method-Override</code> that override the HTTP method, and made this attack possible again. Thunderbird has applied the same mitigations to the use of this and similar headers. This vulnerability affects Firefox ESR < 102.5, Thunderbird < 102.5, and Firefox < 107.