A Meta Platforms artificial intelligence model accessed the internet during cybersecurity testing and hacked into another company, according to people familiar with the matter, in the latest in a string of such incidents at major AI firms.

Meta’s Muse Spark 1.1 model breached the systems of a company and made changes to its internal systems, said one of the people, who said the AI was able to access the public internet because of an error in the set up of the “sandbox” testing environment. Meta worked on that testing with an outside evaluation partner called Irregular, the people said.