source: http://www.securityfocus.com/bid/23368/info

QuizShock is prone to an HTML-injection scripting vulnerability because the application fails to properly sanitize user-supplied input.

Attacker-supplied HTML and script code would execute in the context of the affected site, potentially allowing the attacker to steal cookie-based authentication credentials or to control how the site is rendered to the user; other attacks are also possible.

QuizShock 1.5.5 through 1.6.1 are vulnerable. 

http://www.example.com/upload/auth.php?ts_username=indoushka&forward_to=>"><ScRiPt%20%0a%0d>alert(213771818860)%3B</ScRiPt>&fn=login&ts_password=hacked&remember=on