Sophos EAS Proxy before 6.2.0 for Sophos Mobile Control, when Lotus Traveler is enabled, allows remote attackers to access arbitrary web-resources from the backend mail system via a request for the resource, aka an Open Reverse Proxy vulnerability.
https://www.pallas.com/advisories/sophos_eas_open_reverse_proxy_vulnerability
http://www.securityfocus.com/bid/92351
http://www.securityfocus.com/archive/1/539126/100/0/threaded
http://packetstormsecurity.com/files/138210/Sophos-Mobile-Control-3.5.0.3-Open-Reverse-Proxy.html