Re: Hide extensions for known file types
The issue here has nothing to do with Explorer, but with the data: URL scheme. The attachment never gets to your hard disk, it's a fake. When you attempt to open/download it, you get redirected to the fake Google login. You'll never leave the browser.
AFAIK, it will work on any OS, with any browser supporting the data: scheme.
This is an attack aimed at stealing Gmail credentials (and then probably download user data before using it to mount new attacks).