Battle.net account information has been compromised, with Blizzard urging all members to take steps to secure their information.
According to a notice we've received from Blizzard, there has been "unauthorized access to some Battle.net account information".
All regions outside of China were affected, and the hackers obtained a list of email addresses associated with Battle.net accounts.
The publisher said that "additional information" from North American servers was accessed, including "cryptographically scrambled versions of passwords (not actual passwords), the answer to a personal security question, and information relating to Mobile and Dial-In Authenticators".
"It’s important to note that at this time, Blizzard does not believe this information alone is enough to gain access to Battle.net accounts," the publisher said.
"Based on Blizzard’s investigation to this point, credit card and other customer payment data does NOT appear to have been accessed or affected. As a precaution, however, Blizzard encourages players to change their Battle.net password and any similar passwords used for other purposes."
Blizzard has plugged the security breach and is investigating the hack alongside law enforcement.
According to a public-facing update from Mike Morhaime, the breach occurred this weekend.
Although Morhaime reiterated that Blizzard doesn't believe the hack will enable unauthorised access of individual accounts, all players on NA servers will be automatically prompted to change their passwords and authentication details over the coming week.
Battle.net is Blizzard's umbrella player information and matchmaking system, and includes Diablo III, StarCraft II and World of Warcraft.