Valve has just released version 1.89 on Steam. Below is the change list (containing a little more info than the News update on Steam).
Since in a month or so we'll be at that time of year for games such as Nation Red, you can look forward to another special update around the end of October!
- Local Coop: Added 3 and 4 player local coop support
- On-Line Coop: Players in game will get a chat message if a new player enters the lobby
- On-Line Coop: Team-wide perks are removed from the perk list once one of the players has already chosen them
- On-Line Coop: Chat message history added. Press PageUp/Down or Arrow keys Up/Down to scroll through your chat history
- Leaderboards are easier to navigate from the Statistics Menu. They are now grouped per game mode. Clicking on the flashing arrow cycles between single player, local coop and on-line coop boards.
- Number of zombies in arena is now increased if difficulty setting is higher than default/normal. More zombies means faster and more difficult gameplay but also higher scoring
- Fixed losing Xp level upgrade if a boss was killed in the first minute of the game
- Added fps_max custom maximum frame rate command
- Difficulty level is now saved between game restarts
- Powerup duration time now decreases slower later in game. This makes the game a little easier since powerups last longer compared to the previous version of the game.
- Damage from Minigun and AK47 zombies is reduced by 25% (except in Mission Mode)
- Several smaller bugfixes
- Maximum - In a single game, kill at least one of each zombie boss type while not dropping your health below 100%
- Bullet Rain - Kill two Minigun zombie bosses within two minutes of each other
- Running On Empty - Survive for 15 minutes without holding or picking up any grenades