The vulnerability affects Windows 7, Windows 10, and Windows Server 2012 R2.
This would not be a problem if the mistake had not been detected. Site-released details of the exploit after Microsoft reportedly rejected the provision of an urgent security update. Instead, it was said that an update would be "considered" in a future release. While this suggests a patch is in the way, millions of users may be vulnerable if they do not disable Internet Explorer or point to another application that can open MHT files.