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

Microsoft says the Chinese threat actors Linen Typhoon, Violet Typhoon, and Storm-2603 have been exploiting the ToolShell zero-days.

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.