FUDForum 3.1.0 contains a cross-site scripting vulnerability. An attacker can inject JavaScript via index.php in the author parameter, thereby possibly stealing cookie-based authentication credentials and launching other attacks.
View the template here CVE-2021-27520.yaml
References:
http://packetstormsecurity.com/files/162942/FUDForum-3.1.0-Cross-Site-Scripting.html