Cross-site scripting (XSS) vulnerability in manager/templates/default/header.tpl in ModX Revolution before 2.2.11 allows remote attackers to inject arbitrary web script or HTML via the "a" parameter.
http://www.securityfocus.com/bid/65755
http://secunia.com/advisories/57038
http://seclists.org/oss-sec/2014/q1/431
http://modx.com/blog/2014/01/21/revolution-2.2.11%E2%80%94security-fixes-and-prevent-change-loss