The zero-day vulnerability — which was first disclosed late Saturday — has been exploited by several Chinese state-aligned groups, according to Microsoft.

The National Nuclear Security Administration, which oversees the design and upkeep of America’s nuclear weapons arsenal, was among those whose systems were breached as part of the recent Microsoft SharePoint hack.

The incident has reportedly impacted the servers of federal agencies, schools, and energy companies. Some emergency patches have been deployed. On July 19, Microsoft alerted users that it was experiencing an active cyberattack on its SharePoint servers,