An update has been released for Left 4 Dead 2:

- Fixed another exploit where malicious network packets could severely degrade server performance.
- Fixed a client exploit that could cause long server stalls.
- Fixed a potential crash if a Charger failed to return to valid nav for an extended period of time.
- Fixed a rare hang from ray traces encountering NaN values.

An update has been released for Left 4 Dead 2:

- Blocked an exploit that could forcibly disconnect a player from any server, even when playing a local game.

An update has been released for Left 4 Dead 2:

- Fixed two exploits that could crash remote servers.
- Fixed missing lobby state messages.
- Fixed community server searches not always returning the full set of lowest-ping results.

An update has been released for Left 4 Dead 2:

- Improved the reliability of "mm_dedicated_force_official_servers" to find the lowest ping server across the supplied IPs.

An update has been released for Left 4 Dead 2:

- Fixed several matchmaking lobby exploits.
- The cvar "mm_dedicated_force_servers" now only applies to lobbies with the "Best Available Dedicated" server type as originally intended - for all other lobby types the cvar is ignored. Lobby leaders who wish to force official dedicated server selection due to location or network issues should use the new cvar "mm_dedicated_force_official_servers", which only pulls from available official dedicated servers at the requested IPs.

An update has been released for Left 4 Dead 2:

- Fixed an exploit where reliable network fragments could stall out a server indefinitely.
- Re-enabled uploads by default so sprays will work again.

An update has been released for Left 4 Dead 2:

- Fixed a degenerate case where malformed network packets could delay processing the remainder of the stream, severely impacting server performance.

An update has been released for Left 4 Dead 2:

- Fixed possible corruption of the unreliable network stream during high network loads.
- Increased default command limits to prevent spurious disconnects.

An update has been released for Left 4 Dead 2.

- Added protections against malformed network packets.
- Reduced server-side command limits per client.
- Fixed a regression in script handling of regular expressions.
- Fixed several vulnerabilities and exploits reported via HackerOne.