Researchers say Chinese actors, along with other criminal hackers, exploited a security flaw in SharePoint software widely used by governments and businesses.

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.

Microsoft has issued 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 ...