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 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.

The bugs affecting on-premises builds of SharePoint deployments are officially being exploited by at least two major Chinese nation-state hacking units, the company said. Patches have been issued for all affected versions of SharePoint.