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.
https://m-q-t.github.io/notes/xavier-csrf-to-xss-takeover/
https://codecanyon.net/item/xavier-php-login-script-user-management/9146226