Hackers sponsored by the Chinese state have breached a number of U.S. government institutions, including the agency responsible for overseeing the security of America’s nuclear arsenal, Microsoft warned.

Researchers say Chinese actors, along with other criminal hackers, exploited a security flaw in SharePoint software widely used by governments and businesses.

Suspected Chinese hackers have broken into the email accounts of attorneys and advisers at a powerful Washington, DC, law firm in an apparent intelligence-gathering operation, the firm, Wiley Rein, told clients this week in a memo reviewed by CNN.