The number of companies and organizations compromised by a security vulnerability in Microsoft Corp.’s SharePoint servers is increasing rapidly, with the tally of victims soaring more than six-fold in a few days,

In ongoing hacks, Microsoft says it has identified two Chinese hacking groups taking advantage of a key software flaw.

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.