It seems Tor users better not open DRM files on your Windows computer. Of course it is better not to use windows at all ;-)
Hacker House (a team that also found vulnerabilities in Red Star (north Korea linux OS) made a short movie how it works.
Digital Rights Management (DRM) is a license technology used to prevent spreading of illegal media files. It does this by locking the audio and video files or streams with a encryption key. When you open a file protected by DRM is will ask for the decryption key. This decryption is key is provided by a network server. So users need to be connected to the internet.
The computer will send the real ip address instead of the Tor ip. Of course this is not a new type of attack but still.
See the video below for the demonstration.
Source: https://www.myhackerhouse.com/windows_drm_vs_torbrowser/