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 warned users that hackers used a security flaw in its server software to attack government agencies and businesses around the world. The federal government, along with those in Canada and Australia, has launched an investigation into the hack that targeted SharePoint servers, The Washington Post reported.

A major cyberespionage operation targeting Microsoft's SharePoint server software has compromised about 100 organizations worldwide. The operation exploits a zero-day vulnerability, allowing hackers to install backdoors on affected servers.