The debut of Season 4 for Modern Warfare 3 and Warzone brings additional maps and modes for Multiplayer, the DNA Bomb Killstreak, developments to the bunkers on Urzikstan, and revamps to Warzone's Gulag. Though a Battle Pass featuring three additional weapons has also provided players with alternative armaments to add to their loadouts, the Week 1 Challenges also allow players to acquire the JAK Harbinger aftermarket part for the M4.