source: https://www.securityfocus.com/bid/19460/info

A cross-site scripting vulnerability affects YaBBSE because the application fails to properly sanitize user-supplied input before including it in dynamically generated web content. 

An attacker may leverage this issue to have arbitrary script code execute in the browser of an unsuspecting user. This may help the attacker steal cookie-based authentication credentials and launch other attacks.

http://www.example.com/index.php?action=faqmy&myfaq=yes&id_cat=1&categories=<script>alert("xss")</script>