I got the same email, and had my password invalidated (trying to log in just gives "Incorrect username or password").

To add to the speculation in the linked thread, I _did_ recently reset my password, but it was on 28th February.

I haven't received anything from github, but I use two-factor and oauth tokens, and I don't remember the last time I logged in, let alone changed my password.

I got forced logged and and required a password reset. That was an invalidation.

Oh, then we must have gotten different emails (the one I got was in the linked thread). I didn't know some people got something else!

Same email I got. Strange if not everyone was logged out.