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 says the Chinese threat actors Linen Typhoon, Violet Typhoon, and Storm-2603 have been exploiting the ToolShell zero-days.

The newly discovered flaw in Microsoft's SharePoint software has allowed hackers to target dozens of companies and organizations. Only a partial fix has been issued.

Providing additional updates on the breach, Microsoft said in a blog post on Tuesday that two Chinese nation-state operators, Linen Typhoon and Violet Typhoon, exploited vulnerabilities in the internet-facing SharePoint servers.

Microsoft issued an emergency fix to close off a vulnerability in its SharePoint software that hackers have exploited to carry out widespread attacks on businesses and at least some federal agencies.

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.

A global attack on Microsoft server software used by thousands of government agencies and businesses to share documents within organisations is likely the work of a single actor, a cybersecurity researcher said on Monday.

A major cyber espionage campaign exploiting a previously unknown vulnerability in Microsoft’s self-hosted SharePoint software has compromised nearly 100 organizations, according to cybersecurity firms Eye Security and the Shadowserver Foundation.