Steam's official forums are currently offline for what is being called a maintenance issue, although there's reason to believe that the site's vBulletin forum software may have been hacked. Valve hasn't commented on the issue yet but some gamers noticed a suspicious message on the forum last night that suggests a security breach.
Eurogamer was contacted by a Steam user who said a group known as fkn0wned changed the text on the forum and spammed some user's email addresses. The text reads as follows.
Ever wanted to dominate the servers you play on with guaranteed results, but you were too afraid to cheat because of ban risks? Visit Fkn0wned.com. It's safe, secure and undetected. Along with hacks, we've also got some general discussion sections, hacking tutorials and tools, porn, free giveaways and much more. This site has been conditioned to meet all of your needs in terms of resources so be sure to take a look and tell us what you think. Thanks again, the fkn0wned team.
At this point it's unclear whether any private data like passwords or billing information has been compromised. The breach likely took place sometime last night and as of writing, the Steam's forum is still "down for maintenance."
If we had to take a guess, we'd point the blame at Valve's use of forum software vBulletin which has seen its share of security breaches in the past. Just to be on the safe side, we would advise anyone reading this to change your Steam forum password and perhaps do the same at any other sites where you use the same login credentials.