NEW: We have confirmed that Activision took a specific version of Call of Duty: WWII offline because hackers were abusing a flaw in the game to hack players.
Sources tell us that the issue was a bug that had been patched in other versions of the game, but not on the one for Microsoft Store and Game Pass, which are still offline.

Activision took down Call of Duty game after PC players hacked, says source | TechCrunch
Games giant Activision took down Call of Duty: WWII due to hackers exploiting a flaw in a specific PC version of the game, which led to several players

TechCrunch (techcrunch.com)