Valve's Steam platform has suffered what is being described as the largest information leak in video game history: a 12-terabyte trove containing internal builds of every game uploaded to the service between 2003 and 2013. The material was reportedly accessible via an old, publicly available storage system Valve used before switching to more secure infrastructure, meaning the exposure may not have involved traditional hacking. Because so many publishers used Steam during that period, the breach affects far more than Valve itself, exposing unreleased content from studios of all sizes.

Fans combing through the files have already found beta builds and cut content from major franchises including Call of Duty, Resident Evil, Sonic the Hedgehog, Mirror's Edge, Batman: Arkham Asylum, Dragon Age: Origins and Spore. Discoveries within Valve's own catalogue include an early Portal 2 "bullet time" mechanic, cut Cave Johnson dialogue, and files relating to F-Stop, a long-rumoured camera-based Portal spin-off. The leak also contains material connected to the cancelled Half-Life 2: Episode 3, including references to an ice gun and a "Weaponizer" weapon. Valve has not commented, and given the sheer scale of the data, the full extent of what has been exposed may take considerably longer to emerge.