Last month, Activision posted that they'd "identified and disabled a workaround" within their automated anti-cheat tool, Ricochet. The language of the post is purposefully vague about what actually happened,

A hacker says they've got "thousands upon thousands" of innocent Call of Duty: Modern Warfare 3 and Warzone players banned using an exploit in the game's Ricochet anti-cheat system that's since been resolved.

Call of Duty owner Activision has been fairly open about its mitigation strategies to lessen the number of cheaters in the game using its Ricochet