source: https://www.securityfocus.com/bid/24913/info

Citadel WebCit is prone to multiple input-validation vulnerabilities, including multiple HTML-injection issues and a cross-site scripting issue, because it fails to sufficiently sanitize user-supplied input data.

Exploiting these issues may allow an attacker to execute HTML and script code in the context of the affected site, to steal cookie-based authentication credentials, or to control how the site is rendered to the user; other attacks are also possible.

Versions prior to WebCit 7.11 are vulnerable. 

http://www.example.com/showuser?who=[xss]