Gaming platform Steam, owned by Valve, has been hacked, and the company is currently unsure if users' credit card details have been stolen or not.
Hackers were able to get into a Steam database, which includes encrypted details of many of its users, including credit card information and passwords.
Steam's co-founder and managing director, Gabe Newell, said in a statement: "Our Steam forums were defaced on the evening of Sunday, Nov. 6. We began investigating and found that the intrusion goes beyond the Steam forums. We learned that intruders obtained access to a Steam database in addition to the forums.
"This database contained information including user names, hashed and salted passwords, game purchases, e-mail addresses, billing addresses and encrypted credit card information."
Newell goes on to add that Steam does "not have any evidence that encrypted credit card numbers of personally identifying information were taken by the intruders, or that the protection on credit card numbers or passwords was cracked."
9to5mac reports that Steam is keeping its forums closed down while the investigation into the hack is going on, but the Steam platform is still active.
Newell added that it would be advisable for Steam users to change their passwords and said: "We will reopen the forums as soon as we can. I am truly sorry this happened, and I apologize for the inconvenience."
This hack is embarrassing for Steam, as back in March Newell announced the new Steam Guard, which is designed to offer maximum security for users' accounts. Newell was so confident in the system that he gave out his username and password - to an account that has every game unlocked - to prove that these details were not enough to successfully log in.
Steam now joins the growing list of high-profile companies who have had their Web sites hacked, with Sony, Codemasters and Bioware all suffering as the result of hackers breaking in.