source: https://www.securityfocus.com/bid/5796/info

Problems with PHPNuke could make it possible to execute arbitrary script code in a vulnerable client.

PHPNuke does not sufficiently filter potentially malicious HTML code from news posts. As a result, when a user views a news posting that contains malicious HTML code, the code contained in the posted message would be executed in the browser of the vulnerable user. This will occur in the context of the site running the PHPNuke software.

<IMG SRC="javascript:alert('unsecure')">