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.

Microsoft has observed two named Chinese nation-state actors, Linen Typhoon and Violet Typhoon, exploiting vulnerabilities targeting internet-facing SharePoint servers. In addition, we have observed another China-based threat actor,

A cyber-espionage campaign centered on vulnerable versions of Microsoft's server software now involves the deployment of ransomware, Microsoft said in a late Wednesday blog post.