Developer Infinity Ward took out all vehicles in Warzone on Sunday due to a glitch, which could end entire game sessions. Warzone is the battle royale part of Call of Duty: Modern Warfare, released last year.
This is a problem that occurs when players drive to the boundaries of the playing field. These are shown on the minimap with a clear red dotted line. As soon as it is exceeded, the usual warning follows to return to the combat area.
Normally, that involves a five second countdown timer to return, but players found that timer no longer counted down. Subsequently, players could no longer get out of their vehicle or perform other actions. After a few tens of seconds, an error message about a lost connection to the server follows and the player returns to the main menu. The round is thus ended and so have all the other players in that specific lobby.
Infinity Ward has on Twitter only let you know that the released update results in all vehicles being temporarily removed from Warzone. The developer does not provide further details or an expected date for when the vehicles will make their return.
Update, September 9: Meanwhile, the vehicles back again in game.