CVSS8.7
Severityhigh
WeaknessCWE-178
ExploitedNot in CISA KEV
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
Description
HAX CMS helps manage microsite universe with PHP or NodeJs backends. Prior to version 26.0.0 of HAX CMS PHP, the `saveFile` endpoint validates upload extensions case-insensitively and writes the filename to disk verbatim, but the `.htaccess` rule that forces `Content-Disposition: attachment` on HTML files is case-sensitive. An HTML file uploaded with an uppercase extension (`.HTML`, `.Html`, `.HTM`) is still served as `text/html` but the forced-download header never applies, so the browser renders it inline and executes any embedded JavaScript in the HAXcms origin. This bypasses the mitigation shipped for CVE-2026-22704. Version 26.0.0 contains a fix.