Hackers breach OpenAI using Claude tools, gaining access to employee accounts and the company's internal codebase — attackers initiated a 'harmless' pull request as proof of the hack

A team of white-hat hackers from cybersecurity startup Hackron AI has successfully hacked OpenAI using Claude tools. In an X post on September 18, the team claimed they breached OpenAI's internal codebase on July 25 and gained access to the ChatGPT and Codex accounts of some OpenAI employees. They established proof of the hack via a pull request to OpenAI's private repository before reporting the vulnerabilities to OpenAI. The company reportedly fixed the issue within 14 hours of the report and paid the researchers a $6,500 bounty.

Operating as hackers under OpenAI’s bug bounty program, Hacktron researchers uncovered critical vulnerabilities that granted them access to internal employee tools and the ability to compromise private software repositories. The researchers exploited a single sign-on (SSO) misconfiguration and a Remote Code Execution (RCE) flaw in Discourse, a third-party platform that powers OpenAI’s community discussion forum. The chain of attack was as follows: HEIF upload → libheif heap overflow → RCE → OpenAI SSO flaw → ChatGPT/Codex takeover → connected GitHub → internal PR.

First, the researchers uploaded a malicious HEIF (High Efficiency Image File) image to the forum as a profile picture. When Discourse’s server-side software tried to process the image using an outdated libheif package, it triggered a heap overflow memory vulnerability, causing the library to crash and mismanage internal system memory. The researchers carefully orchestrated the memory crash to achieve remote code execution. After gaining access to the forum's local server environment, the researchers intercepted the server’s environmental configurations and session handling, discovering an SSO flaw in which the forum's authentication system did not adequately validate or isolate user sessions from other OpenAI services.