An update has been released for Left 4 Dead 2.

- Fixed several exploits reported via HackerOne.
- Fixed controller navigation in some menus.
- Fixed not being able to open the train door in Crash Course when playing the Tank Run Mutation.
- Only the original attacker gets credited for damage caused by exploding props.
- Restored the knife's original horizontal swing trajectory.
- Fixed incorrect instructor lesson bindings for the Tank.
- Fixed LDR skybox rendering on low shader settings.

New response criteria:
- "TankActive"- 0 means no Tank aggro, 1 means Tank is aggro.
- "Chapter" - 0 is first map of mission.

New Script Functions:
- "AreAllSurvivorsInBattlefield" - Returns true if all Survivors are in the battlefield
- "GetClosestCharacterWhoIsIT" - Returns the closest character who is IT
- "GetClosestSurvivor" - Returns the closest Survivor to the passed origin
- "GetHighestFlowSurvivor" - Returns the Survivor with the highest flow
- "GetLowestFlowSurvivor" - Returns the Survivor with the lowest flow
- "GetRandomSurvivor" - Returns a random Survivor

Maps and Mutations:

Dead Center
Map 1:
 - Restored window clip-hang bugs that were patched with TLS to re-allow access to the rooftop in Coop mode.
 - Versus: Tank will now only spawn after Survivors have exited the elevator, and no later than leaving the kitchen.
Map 3:
 - Blocked a stuck spot at vending machine alternative path.

Dark Carnival
Map 1:
 - Patched a rarer stuck spot at the swamp's cargo container.
 - Patched an elaborate SI out of bounds exploit.
Map 5:
 - Addressed some issues with "THE MAIN ATTRACTION" Achievement by adding more triggers so it no longer fails if any Survivor disconnects or goes idle while on stage.

Swamp Fever
Map 1:
 - Patched janky ladder near the ferry event.
 - By popular community request the TLS Swamp gator is now canonically named Fred.
Map 2:
 - Blocked a stuck spot behind some rocks at the start near the parachutist.
 - Blocked a stuck spot on a cypress knee near the parachutist area dock.
Map 3:
 - Blocked stuck spots at two sets of cypress knees around the event start area.
 - Versus: Blocked a stuck spot for SI behind a bush to the left of the first bridge upon entering the water.
 - Versus: Blocked a stuck spot for SI in the bush near the lantern/event start.
 - Versus: Improve SI clipping of first ladder outside saferoom to allow drop through a large gap.
 - Versus: Moved a TLS Infected ladder out of the Survivor's way at the start.
Map 4:
 - Versus: Blocked a stuck spot for SI behind a bush in the back of the enclosed hedge area.

Hard Rain
Map 2:
 - Restored a shortcut that was patched with TLS; instead fixed the soft-lock where Survivors cannot progress if one player skipped the elevator.

The Parish
Map 2:
 - Eliminate a stuck spot that a previous ladder patch created.
Map 3:
 - Versus: New ladder in far corner of manhole drop area to fix stuck .
Map 4:
 - Versus: Reduced a jet strike trigger after the balcony drop that previously dealt 25 damage per touch (75 total) to Survivors, down to only 2 damage per touch to behave like the other triggers.

The Passing
Map 1:
 - Blocked a stuck spot in a corner behind a floodlight in the top floor after the alarm cars.
Map 2:
 - Fixed collision issue with clips on the stairs by the saferoom that caused noticeable teleporting when not on a local server.

The Sacrifice
Map 2:
 - Versus: Delete func clip that blocks SI access into end closet.

No Mercy
Map 1:
 - Lift anti-grief kill trigger off the ground to prevent an incap glitch.
 - Versus: Add clip to patch a ladder shortcut at the start.
Map 2:
 - All sets of railings will now appear for all players regardless of graphics settings.

Crash Course
Map 1:
 - Block rare stuck spot between the box wreck and traffic light.
Map 2:
 - Clip to prevent gas cans from falling between finale buses.

Death Toll
Map 3:
 - Blocked a stuck spot at the top of a rock cliff cluster just after the church bus.
 - Blocked a stuck spot between the cliff rocks and the right side of the mandatory house.
 - Versus: Fixed an SI stuck spot on the barricade by the church.

Dead Air
Map 3:
 - Updated clip brushes and navmesh to allow SI players onto a previously blocked pipe that has an Infected ladder leading up to it.
 - Updated clip brushes and navmesh so that Survivors may now enter the hallway next to the end saferoom, which was blocked by a roof clip in the port from L4D1.
Map 4:
 - Fix SI player and AI stuck spot inside the end rubble.

Blood Harvest
Map 2:
 - Versus: Fixed SI stuck beyond the end of tunnel just before end safe room.
Map 3:
 - Fix rare stuck spot in starting saferoom for SI only.
 - Stuck in tree near shed.
Map 4:
 - Versus: Patched fence Infected ladder next to lawnmower room.

Cold Stream
Map 2:
 - Fix stuck next to military truck leading to barricade.
 - Fix two stuck spots behind the long hedges on the right of after the military truck leading to barricade.
 - Fix a regression with easy event skip clip and a stuck clip nearby.
Map 3:
 - Enlarged a stuck clip to fully fix it.

The Last Stand
Map 2:
 - Simplified finale difficulty scaling so it is now only increased on Advanced and Expert difficulties rather than scaling each difficulty differently; the intention is to curb player fatigue and confusion in addition to bringing it more in line with expectations from other finales.
 - Lowered the number of required gas cans in Single Player by 25% to help compensate for only having bot teammates; Easy/Normal difficulty now require 6, and Advanced/Expert difficulty now require 9.
 - The gas can requirement in Multiplayer modes now increases by 1.5x per difficulty; Easy/Normal difficulty now require 8, and Advanced/Expert difficulty now require 12.
 - Versus: Fixed an out of bounds exploit to get under a cliff side.
 - Versus: Fixed a stuck spot between a tree cluster and Versus-only fence at the cliff that overlooks the beach.

Tank Run:
 - The first map of a Campaign will now spawn two Tier 1 weapons near the start area if no other Tier 1's are nearby.
 - Car alarms will now spawn a Tank if triggered.
 - Disabled water slowdown for all maps.
 - Set Survivor revive health to 50.
 - Added auto self-revive mechanic with a delay based on the "survivor_revive_duration" Cvar (default 5 seconds).
 - Slight buff to pistol and melee damage against the Tank.
 - Fixed issue where the sacrificing player would get auto-revived after restarting the generator.
 - Fixed issue where the finale would result in a failed screen if players that jumped off of the bridge to restart the generator got incapped.
 - Fixed issue where players going idle, switching characters or leaving the game would break the auto-revive for that Survivor.
 - Fixed issue if a Tank was deleted while being biled, it would break the script.
 - Fixed issue where Tanks would not retain their slowdown when biled, if they were hit with another vomit jar while already being biled.
 - Fixed issue where Survivors could get instantly revived when hit with a car.

Death's Door:
 - Enabled heartbeat sound when under 25% health.
 - Enabled B&W state when at 1 permanent HP.
 - Fixed heartbeat sound when taking over bot.
 - Fixed Fallen Survivors being able to drop medkits.
 - Fixed temporary health decay in the safe room, loading players will no longer decay temp health.
 - Defibrillator now heals 1 permanent - 99 temporary HP (still B&W).
 - Safe room respawn now heals 24 permanent - 26 temporary HP (only heartbeat sound).
 - Safe room transition now heals 80% of the missing HP to half health of living Survivors, e.g. 1 to 40 (no health effects).
 - Fixed an issue that caused the mission to fail for Sacrifice type finales when the player presses the final button.

Versus Survival:
 - Thickened clips and other map-specific fixes to dramatically reduce stuck spawns.
 - Made it auto-trigger any outputs on the entity used to start Survival if the pre-round timer expires.

Taaannnk!!:
 - Thickened clips and other map-specific fixes to dramatically reduce stuck Tank spawns.
 - Players no longer need to wait for incapped Survivors in order to progress at areas like elevators.

L4D1 Coop & Survival & Versus:
 - Set the claw viewmodels for the L4D1 SI to the proper L4D1 models for L4D1 Versus.
 - Disabled water slowdown for L4D1 Survival.
 - Defibrillators now convert to pain pills instead of medkits; previously, when converted to medkits the game kept trying to spawn more defibs which led to an over-saturation of medkits.
 - Changed noise levels for running and talking to their values from L4D1; this will make it slightly harder for Common Infected to notice Survivors, like their L4D1 counterparts.
 - Changed to use much more accurate L4D1-like looking ragdolls.