NEW YORK (AP) — Microsoft has issued 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 released a patch Monday for SharePoint Server 2016 that protects customers against a pair of vulnerabilities, which have been widely exploited in a wave of cyberattacks known as “ToolShell.”

Microsoft has released security updates addressing the exploited vulnerabilities and urged all customers to apply patches without delay.