[spencerhakim]

Steam has a hidden debug console that allows users to rollback any game to any previous release via the `download_depot` command. It's not remotely as user friendly as when a publisher adds an old version of a game as a beta branch that can be easily switched to in the UI, but as far as I know there's no way to prevent its use.

[asmor]

that only works as long as the old depot is still there, and it usually is just to make it easier to delta update.