Every Call of Duty game has had its fair share of glitches and while Modern Warfare 3 has been outside of that category for quite a while, its time has come.
MW3 has finally been exploited enough to the point to allow challenge a.k.a. hacked lobbies to exist online. These lobbies allow users to illegally gain heaps of experience and prestige, have unlimited ammo, spawn vehicles and the list extends far from that. While this is all cool when done in a private lobby, some feel the need to take it to the public servers, where it becomes more of a problem.
Now who would be most likely to blame? Users of he xk3y and Wasabi360 ODDEs might have something to do with this.