Cross-site scripting (XSS) vulnerability in rss/index.php in PHP iCalendar 2.22 and earlier allows remote attackers to inject arbitrary web script or HTML via the cal parameter.
https://exchange.xforce.ibmcloud.com/vulnerabilities/27448
http://www.vupen.com/english/advisories/2006/2597
http://www.securityfocus.com/archive/1/438621/100/0/threaded