Valve has notified users their personal information — included encrypted credit card information — has been compromised following an intrusion that recently took place.
The Steam forums were taken offline earlier this week after they were defaced by hackers (as pictured below). There was no indication at the time that anything significant had taken place beyond users finding an exploit in the forum software valve uses. Visiting them continues to bring up the same message: “The Steam Forums are temporarily offline for maintenance. Your patience is appreciated.”