GHSA-vcrw-4xvv-jh49 MantisBT: Reflected XSS in admin/install.php via unescaped printf

• Packagist mantisbt/mantisbt: < 2.28.4 → fixed in 2.28.4

MantisBT 2.28.3 and earlier contains six reflected XSS injection points in `/admin/install.php`. User-supplied parameters are echoed into HTML without escaping via an unescaped printf format string. No authentication is required. A Content Security Policy (script-src 'self') prevents inline JavaScript execution, but the CSP is missing a form-action directive, allowing exploitation via credential-phishing form injection and open redirects. Impact • Credential phishing: Attacker crafts a URL that renders a fake login form on the real MantisBT admin page. Admin credentials are submitted to an attacker-controlled server. • Open redirect: Victim is silently redirected to a phishing or malware site. • UI manipulation: CSS injection can hide legitimate page content and overlay attacker-controlled HTML, enabling social engineering. Patches • https://github.com/mantisbt/mantisbt/commit/297773fbb238c39a153bd888431b41a176132098 Workarounds Remove the `/admin` directory, as recommended in the Admin Guide Resources • https://mantisbt.org/bugs/view.php?id=37103 • related advisory GHSA-77x8-3v3h-hrhv Credits McCaulay Hudson (@_McCaulay) of watchTowr