Steam deployed a buggy caching configuration while trying to resolve a DDoS attack that hit the popular gaming platform on Christmas Day, which resulted in the personal information of some users being displayed to others.
Many users started complaining on December 25 that when they accessed the “Account Details” section of their Steam Store account they were seeing other users’ information instead of their own. Many also reported that language settings had changed in their accounts.
Customers, some of whom believed the incident might have exposed the details of millions of users, were unhappy that they hadn’t received clarifications and an apology. Valve, the company behind Steam, finally provided an explanation and apologized on Wednesday.
In a statement detailing the incident, the company said DDoS attacks against the Steam Store and Steam in general typically don’t impact users. However, since this attack was launched during a Steam Sale, traffic to the Steam Store increased by 2000 percent compared to average traffic recorded during such periods.
To address the issue, the firm that handles web caching for Steam deployed a couple of caching configurations, one of which incorrectly cached traffic for authenticated users. This resulted in responses getting mixed up and users seeing content generated for others.
According to Valve, the incident impacted roughly 34,000 users who accessed Steam Store pages containing private information between 11:50 PST and 13:20 PST on December 25. Users who did not access their account details page or checkout page during this timeframe are not affected.
Valve said the exposed information included the user’s billing address, purchase history, last four digits of the Steam Guard phone number, partial credit card number, and email address. The company has clarified that the cached requests did not include passwords, full payment card numbers or other information that could be used to log into accounts or complete a transaction.
“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 said.