The revelation comes as US officials are continuing to grapple with the fallout of a massive Chinese cyberespionage campaign known as Salt Typhoon that gave officials in Beijing access to private texts and phone conversations of an unknown number of Americans.
The update is the latest development in a massive hacking operation that has alarmed national security officials, exposed cybersecurity vulnerabilities in the private sector and laid bare China's hacking sophistication.
The company has released security updates to protect customers running Exchange Server, and encourages all Exchange Server customers to apply these updates immediately.