Required updates to Team Fortress 2, Counter-Strike: Source and Day of Defeat: Source are now available. Please run hldsupdatetool to receive the updates. The specific changes include:

Source Engine Changes (CS:S, DoD:S, TF2)
- Disabled clients loading server plug-ins unless the plug-ins are signed by Steam or the client is running in insecure mode.
- Added a checkbox to the Options->Audio dialog to control muting the audio when the game window is in the background.

Counter-Strike: Source
- Fixed crash in custom maps using the trigger_camera entity.

Team Fortress 2
- Fixed another bug in the Steamworks internal stats reporting.
- Updated the localization files.