The Authen::ExternalAuth extension before 0.11 for Best Practical Solutions RT allows remote attackers to obtain a logged-in session via unspecified vectors related to the "URL of a RSS feed of the user."
https://exchange.xforce.ibmcloud.com/vulnerabilities/77213
http://www.securityfocus.com/bid/54681
http://secunia.com/advisories/50060
http://lists.bestpractical.com/pipermail/rt-announce/2012-July/000208.html