If you have Blizzard accounts, now would be a good time to reset your password and other security details (like security questions, etc.).
Blizzard's security team found that its internal network has been illegally accessed, and answers to personal security questions, authenticator data and cryptographically scrambled Battle.net passwords have found their way into the perpetrator's hands. The team is confident, however, that the compromised data isn't enough to give the attacker access to user accounts. Right now there is no lead if the attackers got their hands on financial data, but then again you can't rule that out.
Blizzard President Mike Morhaine recommends that users update their passwords all the same, and I couldn't agree more.
You can update all of that account info from the source link below.