At least three China-based hacking teams have been exploiting a previously unknown flaw in Microsoft SharePoint since at least July 7, the company said in a blog post. Why it matters: Microsoft and security researchers didn't uncover the vulnerability until this past weekend,

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

At least two Chinese hacking groups were using security flaws in SharePoint, a popular collaboration software, to breach systems, Microsoft said.