In an alert issued on Saturday, Microsoft said the vulnerabilities apply only to SharePoint servers used within organizations. It said that SharePoint Online in Microsoft 365, which is in the cloud, was not hit by the attacks.

Hackers have exploited vulnerabilities in Microsoft’s SharePoint software, placing tens of thousands of on-premises servers used by global businesses and agencies at risk. Microsoft issued an alert on Saturday disclosing that it was aware of “active attacks,” and that it was working to patch the zero-day exploit.

Microsoft said the company has been "coordinating closely with CISA, DOD Cyber Defense Command, and key cybersecurity partners around the world throughout our response."