source: http://www.securityfocus.com/bid/7310/info

It has been reported that user-supplied input to phPay is not sufficiently sanitized. This lack of sanitization provides an opportunity for an attacker to launch cross-site scripting attacks.

It is possible for a remote attacker to create a malicious link containing script code that will be executed in the browser of a legitimate user.

Any attacker-supplied code will be executed within the context of the website running phPay.

While this vulnerability has been reported to affect phPay version 2.02, previous versions may also be affected. 

http://www.example.com/search.php?sess=your_session_id&lookfor=<script>alert
(document.cookie)</script>