The get_referers function in /opt/ws/bin/sblistpack in Sophos Web Appliance before 3.7.9.1 and 3.8 before 3.8.1.1 allows remote attackers to execute arbitrary commands via shell metacharacters in the domain parameter to end-user/index.php.
http://www.sophos.com/en-us/support/knowledgebase/119773.aspx