Exact same thing for a few days.

Clicking Facebook-login, then I'm brought to facebook to enter credentials. After pressing "login" I am brought to a completely white page at the adress:

https://www.facebook.com/login.php?login_attempt=1&fbconnect=1&display=page&next=https%3A%2F%2Fimgur.com%2Fsignin%2Ffacebook&req_perms=user_photos%2Cemail&legacy_return=1

or without hexcode:

https://www.facebook.com/login.php?login_attempt=1&fbconnect=1&display=page&next=https;//imgur.com/signin/facebook&req_perms=user_photos,email&legacy_return=1 

If I manually return to imgur or use the back-button, I am still logged out. This worked fine for me about a week ago.