Cross-site scripting (XSS) vulnerability in auth.php in Pineapple Technologies QuizShock 1.6.1 and earlier allows remote attackers to inject arbitrary web script or HTML via encoded special characters in the forward_to parameter, as demonstrated using "<"<".
https://exchange.xforce.ibmcloud.com/vulnerabilities/33523
http://www.vupen.com/english/advisories/2007/1319
http://www.securityfocus.com/bid/23368
http://securityreason.com/securityalert/2554