Clearswift MIMEsweeper For Web (a.k.a. WEBsweeper) 4.0 through 5.1 allows remote attackers to bypass filtering via a URL that does not include a .exe extension but returns an executable file.
https://exchange.xforce.ibmcloud.com/vulnerabilities/23867
http://www.securityfocus.com/bid/15982/
http://www.securityfocus.com/archive/1/419904/100/0/threaded