Content creators will now package their maps into a single .VPK file, which users can install with a simple double-click. Players can manage their add-ons and campaigns within the game. Valve has also added matchmaking, leaderboards and auto-update/download support for custom maps.

Check below for the full patch notes:

Client

• Removed an infinite ammo exploit for molotovs
• The team swapping issue in Versus has been fixed

• Players download third party campaigns as single .VPK file
• Players can manage and select add-on maps and campaigns via game UI
• Added matchmaking support and download/update prompt for add-on campaigns
• Custom campaign support in Leader boards
• If not already registered, left4dead.exe registers .VPK extension to allow automatic install of add-ons
• Servers and the steam API have been extended to allow servers to send up a list of keys for matchmaking up to 1200 bytes in size

• Fixed missing fgd error
• Added vpk.exe command line tool for extracting, creating, and appending .VPK files
• Removed info_versus (not used)
• Added info_gamemode which fires outputs for Coop, Versus or Survival depending on what game mode the map is loaded in
• Updated tutorial_standards example map, repackaged as 'Dead Line' campaign example add-on
• Sample content now includes source files for official maps