Updates to CS:S, HL2, and the Source engine have been released. The updates will be applied automatically when your Steam client is restarted. The specific changes include:

Counter-Strike: Source

• Removed FCVAR_ARCHIVE from cl_minmodels
  
• Added a workaround for linux servers sometimes being frozen after changelevel
  
• Linux dedicated server -condebug captures all console output now
  
• Fixed an exploit when joining a team that could spawn live spectators
  
• Fixed mp3 player advancing more than 1 song during level transitions

Half-Life 2

• Fixed bug where NPCs would ignore hintbrushes that should block line of sight

Source Engine

• Fixed really long game directories not being able to upload game statistics
  
• Fixed listen server host not being able to hear sounds from bsp .zip files
  
• Fixed demo smoother not being able to select samples in certain demo files
  
• Fixed partial-HDR exploit in DX7 allowing wireframe materials

News Source: Steam News