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:

Death Toll campaign released

• Fixed scoring in finale
  

Blood Harvest; The Bridge

• Infected will spawn in front of the survivor team on their way to the Safe House.
  
• Added Infected spawn locations on the hill by the Safe House.
  

Blood Harvest: The Train Station

• Fixed exploit that allowed Infected team to trigger the onslaught.