source: http://www.securityfocus.com/bid/9890/info

It has been reported that the Mambo 'index.php' script is prone to a cross-site scripting vulnerability. This issue is due to a failure of the application to properly validate user supplied URI input. This issue could permit a remote attacker to create a malicious link to the vulnerable application that includes hostile HTML and script code. If this link were followed, the hostile code may be rendered in the web browser of the victim user.

http://www.example.com/index.php?return=[XSS]