I'm pleased to announce the release of Metamod:Source 1.8.4. This is a small bug-fix release to work with the latest Left 4 Dead updates.
Full changelog:
* Added support for Alien Swarm (User Changes:
* Updated support for latest Left 4 Dead 1
(bug 4681).
Developer Changes:
* Updated TF2 custom kill defines
(bug 4682).
http://forums.alliedmods.net/showthread.php?t=141971