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

A series of cyberattacks targeting Microsoft collaboration software, specifically SharePoint, have been linked to Chinese hackers and threat actors.

Hours after Microsoft revealed hacking groups affiliated with the Chinese government have been exploiting a flaw in its SharePoint software, Bloomberg News reports that the National Nuclear Security Administration has also been breached in the attacks.

Microsoft has released a critical patch for a security flaw in its SharePoint software. Hackers actively exploited this vulnerability, targeting businesses and US government agencies. The company issued the fix between July 19 and 20.

State CISOs in North Carolina and Arizona said their teams began work immediately to ensure on-prem SharePoint systems were secure, following the recent disclosure of an active zero-day exploit.

Dubbed a “zero-day” because it leverages a previously undisclosed digital weakness, the hacks allow spies to penetrate vulnerable servers and potentially drop a backdoor to secure continuous access to victim organisations.

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.