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 confirmed “active” cyberattacks exploiting vulnerabilities in on-premises SharePoint Servers and released emergency patches for several versions of the systems.

Microsoft has issued an emergency fix in its SharePoint software after hackers began exploiting a vulnerability to carry out widespread cyberattacks. On Saturday, the company issued an alert saying organizations using the software should apply security updates immediately. SharePoint Online in Microsoft 365 was not hit by the attacks.