Dropbox has been hacked. Hackers are leaking username and passwords. Changed your password now. If you don’t have two factor authentication activated, it’s a good idea to do so.
UPDATE: Dropbox has denied it was hacked. A statement by a Dropbox representative claims:
Dropbox has not been hacked. These usernames and passwords were unfortunately stolen from other services and used in attempts to log in to Dropbox accounts. We’d previously detected these attacks and the vast majority of the passwords posted have been expired for some time now. All other remaining passwords have been expired as well.
Take it for what it’s worth. These password leaks are getting more common and more tiresome.
Two. Factor. Authentication.