Cybersecurity stocks are slumping in premarket trading on Friday as the AI disruption trade returns after a Fortune report said Anthropic is testing a new AI model that "poses significant cybersecurity risks."

According to the report, Anthropic is "developing and has begun testing with early access customers a new AI model more capable than any it has released previously," the company said, following a data leak that revealed the model's existence. 

An Anthropic spokesperson said the new model represented "a step change" in AI performance and was "the most capable we've built to date." The company said the model is currently being trialed by "early access customers."

Descriptions of the model were inadvertently stored in a publicly-accessible data cache and were reviewed by Fortune.

A draft blog post that was available in an unsecured and publicly-searchable data store prior to Thursday evening said the new model is called "Claude Mythos" and that the company believes it poses unprecedented cybersecurity risks.