The IICAClient interface in the ICAClient library in the ICA Client ActiveX Object (aka ICO) component in Citrix Online Plug-in for Windows for XenApp & XenDesktop before 12.0.3 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted HTML document that triggers the reading of a .ICA file.
http://support.citrix.com/article/CTX125976
http://secunia.com/advisories/40821
http://secunia.com/advisories/40819
http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=875