A critical vulnerability in on-premise SharePoint servers allowed state-backed hackers to breach governments and institutions worldwide. Experts are questioning why more hasn't been done or said.

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.

The bugs affecting on-premises builds of SharePoint deployments are officially being exploited by at least two major Chinese nation-state hacking units, the company said. Patches have been issued for all affected versions of SharePoint.