Valve’s Steam PC gaming service had a bit of a rough Christmas. Some type of server issue caused users to be presented pages as if they were logged in as other people. This might seem odd, but it was actually fairly dangerous, as credit card info, as well as addresses could be found depending on how the problem presented itself. Eventually Valve took the entire store down to handle the problem, and while some smaller issues have lingered, overall the major glitches were worked out quickly.
However, the biggest talking point after the whole thing was Valve’s odd silence on the topic. Little was said about what happened, how widespread the impact was, and what Valve was doing to rectify the security breach. That silence has been broken today with a comprehensive post related to the issues.
“On December 25th, a configuration error resulted in some users seeing Steam Store pages generated for other users,” reads the post describing the issue itself. “Between 11:50 PST and 13:20 PST store page requests for about 34k users, which contained sensitive personal information, may have been returned and seen by other users.
We apologize to everyone whose personal information was exposed by this error, and for interruption of Steam Store service.
“The content of these requests varied by page, but some pages included a Steam user’s billing address, the last four digits of their Steam Guard phone number, their purchase history, the last two digits of their credit card number, and/or their email address. These cached requests did not include full credit card numbers, user passwords, or enough data to allow logging in as or completing a transaction as another user. If you did not browse a Steam Store page with your personal information (such as your account page or a checkout page) in this time frame, that information could not have been shown to another user.
“Valve is currently working with our web caching partner to identify users whose information was served to other users, and will be contacting those affected once they have been identified. As no unauthorized actions were allowed on accounts beyond the viewing of cached page information, no additional action is required by users.”
Valve then describes exactly how the issue occurred in the first place, saying “Early Christmas morning (Pacific Standard Time), the Steam Store was the target of a DoS attack which prevented the serving of store pages to users. Attacks against the Steam Store, and Steam in general, are a regular occurrence that Valve handles both directly and with the help of partner companies, and typically do not impact Steam users. During the Christmas attack, traffic to the Steam store increased 2000% over the average traffic during the Steam Sale.
“In response to this specific attack, caching rules managed by a Steam web caching partner were deployed in order to both minimize the impact on Steam Store servers and continue to route legitimate user traffic. During the second wave of this attack, a second caching configuration was deployed that incorrectly cached web traffic for authenticated users. This configuration error resulted in some users seeing Steam Store responses which were generated for other users. Incorrect Store responses varied from users seeing the front page of the Store displayed in the wrong language, to seeing the account page of another user.”
Valve took the entire store down as soon as they realized what was going on. They then reconfigured their cache system and made sure it was working properly before deploying it and bringing the store back online. The post closes by saying “We will continue to work with our web caching partner to identify affected users and to improve the process used to set caching rules going forward. We apologize to everyone whose personal information was exposed by this error, and for interruption of Steam Store service.”