A team of three independent security researchers at Hacktron says it took less than 72 hours for them to hack into OpenAI employee accounts using Anthropic’s Claude Opus 4.8 and 5, the Wall Street Journal reports. They were able to access OpenAI’s GitHub repository, called “Monorepo,” which reportedly contains “OpenAI’s algorithmic secrets,” according to the Wall Street Journal’s sources.

They stopped short of accessing internal code in Monorepo themselves, but sent a pull request from an employee’s Codex account to prove they gained access. They were able to get in through Discourse, the third-party service that hosts OpenAI’s community forums, by exploiting an issue with the system it uses to process HEIF images. According to Hacktron, Claude Opus 5 launched in the evening on July 24th, and by 10AM the next day they had used it to achieve RCE on Discourse Cloud and accessed OpenAI’s instance.

Their HEIF Heist project took “only one or two days” to adapt to different companies, including OpenAI, Slack, Meta, GitHub Ent, Rails, Next.js, ImageMagick and others, using less than $3,000 in tokens, and to their knowledge, was only detected by one target, Shopify. The vulnerabilities Hacktron reported to Discourse and OpenAI have since been fixed, and Hacktron says OpenAI paid it $6,500 for finding the bug, but as Hacktron CTO Mohan Pedhapati said to the WSJ, “I don’t think we are as strong as Chinese threat actors… We’re just three guys with Claude and Codex subscriptions.”