Microsoft Corp. said a Chinese hacking group is exploiting security vulnerabilities in the company’s SharePoint servers to deploy ransomware, following a cyberattack discovered last week that has affected hundreds of entities around the world.

Microsoft said in a post on its website on Saturday that it was “aware of active attacks targeting on-premises SharePoint Server customers by exploiting vulnerabilities.” SharePoint is a Microsoft platform that allows customers to manage and share documents within their organizations.

Microsoft has warned that Chinese state-sponsored hackers have breached its SharePoint software used by the US agency responsible for maintaining and modernizing the nation’s stockpile of nuclear weapons, according to a report.

Unknown attackers exploited a “significant vulnerability” in Microsoft’s SharePoint collaboration software, hitting targets around the world.

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.

Microsoft has issued a stark warning about a recent cyberattack targeting critical infrastructure, including the U.S. National Nuclear Security Administration (NNSA), exposing vulnerabilities in its SharePoint software.

South Africa’s National Treasury is among at least 400 entities worldwide to be affected by a hack of Microsoft’s SharePoint document management system.

The zero-day vulnerability — which was first disclosed late Saturday — has been exploited by several Chinese state-aligned groups, according to Microsoft.

A warning has been issued to Microsoft users detailing a cybersecurity flaw that allowed hackers to access its SharePoint servers, the U.S. Cybersecurity and Infrastructure Security Agency (CISA) announced.

Several entities in South Africa have been compromised by hackers who exploited a security vulnerability in Microsoft Corp’s SharePoint servers, according to Eye Security, the cybersecurity