Is there anybody who didn’t see this coming? Following a pretty stuffy announcement back in May that Battle.net accounts could not be hacked (particularly when it’s linked to an Authenticator), Blizzard have made a more humble announcement that their servers have been hacked:
Some data was illegally accessed, including a list of email addresses for global Battle.net users, outside of China. For players on North American servers (which generally includes players from North America, Latin America, Australia, New Zealand, and Southeast Asia) the answer to the personal security question, and information relating to Mobile and Dial-In Authenticators were also accessed. Based on what we currently know, this information alone is NOT enough for anyone to gain access to Battle.net accounts.
Everyone on the North America server will have a forced password reset in the next few days. You can read more details about what happened here.