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.