The yellow access key cards in Warzone are the reward for finishing the Outbreak mission started at the Containment Monitor Station. Land at shipwreck or whatever area is currently an outbreak area on Verdansk. Find the Containment Monitor Station which looks just like a trials station from Cold War Zombies. Start the outbreak mission from the station and kill all the zombies. The last zombie drops the yellow access card. The yellow crate is styled after the loot crates from the Call of Duty Black Ops Cold War Zombies game mode. Obtain the yellow access keycard and follow the on screen directions to the loot crate it opens. Inside the loot crate will be a huge amount of cash, some weapons, armor, and a scorestreak!
Containment Monitor Stations
Further more, the Containment Monitor Stations have been updated persistently through out the outbreak event and now contain certain unique score streaks that may be purchased for ground loot cash. For example, now players can purchase the RCXD, Advanced UAV , Foresight, and Self revive. Players can also purchase a Bombardment Strike for the cost of a yellow key card.