Multiple cross-site scripting (XSS) vulnerabilities in GuppY before 4.6.28 allow remote attackers to inject arbitrary web script or HTML via the (1) "an" parameter to agenda.php or (2) cat parameter to mobile/thread.php.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.