The company said on Friday night that the federal government had ordered limits on its Mythos and Fable 5 A.I. systems, citing national security concerns.

The flaw, which Meta said it had fixed, allowed anyone to take over accounts using a bug in the company’s new artificial intelligence software.

Encryption systems rely on “random” numbers, but conventional computers can’t generate them perfectly. New research shows that quantum physics can.

Called Claude Fable 5, it is twice as expensive as the company’s previous flagship system.

Researchers at the University of Toronto showed how hackers could use artificial intelligence to create a program that could target any known flaw in the world’s computers.