wtf tumblr?

Tumblr forcibly logged me out, and refuses to let me log in via a webbrowser unless I change my password. Though it doesn't seem to have any problem to let me log into my account via the Android app.

Admittedly I haven't changed my password in a while, but still this is obnoxious behavior, in particular since they did not bother to sent me an email or such to explain or alert me to anything.