A China-based hacking group is deploying Warlock ransomware on Microsoft SharePoint servers vulnerable to widespread attacks targeting the recently patched ToolShell zero-day exploit chain.

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.

Ransomware has officially entered the Microsoft SharePoint exploitation ring. Late Wednesday, in an update to its earlier warning, Redmond confirmed that a threat group it tracks as Storm-2603 is abusing vulnerable on-premises SharePoint servers to deploy ransomware.