Xavier PHP Management Panel 3.0 is vulnerable to Reflected POST-based XSS via the username parameter when registering a new user at admin/includes/adminprocess.php. If there is an error when registering the user, the unsanitized username will reflect via the error page. Due to the lack of CSRF protection on the admin/includes/adminprocess.php endpoint, an attacker is able to chain the XSS with CSRF in order to cause remote exploitation.
