This happened to me as well. Perhaps we should post things that we've done that could be the cause and see if we find a common denominator. Here's what I can think to mention that might be pertinent.

I have a unique (for TmB only), randomly generated password, however I use lastpass to manage it. I'm moving away from this service to keepass, in case it's the culprit
I ran the UVC wallet last night, however it was in a VM.
I've accessed my TmB account from two separate computers as well as a Android tablet. However, I trust all the software I have installed, and don't use any cryptocurrency helper software/extensions/apps (which are the most likely to be infected).