Software security researchers used Anthropic’s Claude AI platform to hack OpenAI’s ChatGPT tool, adding to mounting concerns about the vulnerability of leading large language models to cyberattacks. 

Researchers from Hacktron AI, an independent AI security platform that tests software code, disclosed the breach in a blog post on Sunday. They said they used Claude to gain access to an OpenAI employee’s ChatGPT account, enabling Hacktron AI to retrieve key data on where the source code was stored and managed. They also accessed an OpenAI discussion forum.

“The entire timeline from initial discovery to access to OpenAI repo access took place in less than 72 hours,” Hacktron AI said in the post.

The Hacktron AI team reported the intrusion to OpenAI, which responded promptly and paid researchers a $6,500 bounty, Hacktron AI said in its blog post. 

“We immediately reported the initial vulnerability to OpenAI and Discourse and worked with them to coordinate the patch. We appreciate their attention to detail and fast resolution of this issue,” the researchers wrote. 

The incident was first reported by The Wall Street Journal.

“We thank the researchers for contacting us and sharing their findings. We narrowed the permissions on Community sign-in tokens and revoked affected tokens and sessions,” OpenAI said, according to the Journal. 

Anthropic and OpenAI did not immediately respond to requests for comment. 

The breach comes as AI’s capabilities and vulnerabilities have been thrust into the spotlight, with leading tech developers calling for a slowdown in building AI platforms due to concerns that they could harm people. In July, OpenAI revealed that its bots had collaborated to hack another AI developer, Hugging Face, after escaping a testing environment.

In a recent interview with CBS News, Anthropic CEO Dario Amodei said he sees “real dangers” around AI, citing the Hugging Face hack as a warning sign. In a Sept. 12 essay, he also wrote that the entire tech industry must work together to “slow the pace” of AI development.