I'm using azure active directory B2C as a login priovder with episerver 11, is there any way to bulk log out all users from episerver?
Not that I've heard of at least. Would be a cool feature to build though. A bit tricky especially with federated login.
If you're using cookies to store a auth token, you could try to alter its hashing method so that all cookie values become invalid.
I guess you could add some extra layer that you can also check against and clear data in that layer "on bulk logout" and then send any users part of the clearing through the signout process when they make the next request.