A statement was published on July, 6th 2017 by the German BKA about 500 million user data being found on an underground economy platform.
BKA handed the data over to Hasso-Plattner-Institute. At the website https://sec.hpi.de/leak-checker/search? concerned users can provide their email address to find out if their account data is part of the database.
What shall I do if my account is hacked?