Microsoft is issuing an emergency fix to close off a vulnerability in Microsoft’s SharePoint software that hackers have exploited to carry out widespread attacks on businesses and at least some federal agencies.

Several Chinese-linked hacker groups exploited a critical security flaw in Microsoft’s SharePoint server software, the company confirmed Tuesday. The breach, first detected by cybersecurity startup Eye Security,

The tech giants have evidence that Chinese hackers are exploiting the new bug, but warned "multiple actors" are also hacking into affected SharePoint systems.