Alright, Who did it.
Valve has released an update to fix most of the major map exploits. This will force all players to complete certain tasks before they can proceed further. I suspect there was an overwhelming amount of players petitioning to valve for the fixes. This update will also effect the way you play in XPMod as you will no longer be able to skip some events or climb past some areas. According to valve, this is a start in a long series of updates.
Left 4 Dead 2 Update Released
Updates to Left 4 Dead 2 have been released. The updates will be applied automatically when your Steam client is restarted. The major changes include:
Left 4 Dead 2
Encore mutation: Last Man On Earth
Fixed some missing particle declarations for the Cold Stream campaign
The following map fixes are the first of a series of exploit fixes coming. These will appear on the Xbox 360 in a future update.
Dark Carnival: The Fairgrounds
Survivors can longer get onto the elevated track.
Infected players can no longer block the carousel gate.
Dark Carnival: The Coaster
Survivors can no longer skip the roller coaster crescendo event
Survivor can no longer use shortcuts on the roller coaster
The Parish: The Park
Survivors can no longer skip the bus station crescendo event
The Parish: The Cemetery
Survivors can no longer skip interiors by jumping over a fence or getting onto rooftops