Last year, the Department of Homeland Security released a scathing report detailing Microsoft’s mistakes during a 2023 hack in which China stole thousands of emails from top government officials. Two years before that, China-linked cyberattackers compromised more than 250,000 Microsoft Exchange servers.

The company said state-backed hacking groups were breaching systems through flaws in SharePoint, which is used by the U.S. government and companies around the world.