Reports online indicate that Steam broke its concurrent user record over the holidays reaching as many as 8,357,541 concurrent users on December 28. Steam has not sent out any official release on the matter, but it appears the record has been bested. It's not the first time that the 8 million barrier was reached, but as is typically the case the record was broken during the height of a sale. As you'd expect Dota 2 was the most played game at the time followed by Counter-Strike: Global Offensive, Team Fortress 2, Football Manager 2015 and The Elder Scrolls V: Skyrim.
Thanks, Blue's News.