The Bunker was a weapons dealing site on the Deep Web that had a possibility of containing a Red Room key. After the 2.0 update of Welcome to the Game, the website was shut down by the the FBI, IRS, ICE, and the DEA.
The most likely method of getting a key on this site was by clicking the '8" at the bottom of the page that would download a .txt document labeled "doomsday.txt" to your desktop.