Cross-site scripting (XSS) vulnerability in system/index.php in ExpressionEngine 1.6.4 through 1.6.6, and possibly earlier versions, allows remote attackers to inject arbitrary web script or HTML via the avatar parameter.
https://exchange.xforce.ibmcloud.com/vulnerabilities/49359
http://www.securityfocus.com/archive/1/502045/100/0/threaded