How We Took Over ChatGPT Accounts
Simon Willison summarises Parameter Labs' ChatGPT account takeover chain against the HTML previews (formerly Canvas) sandboxed iframe. A postMessage handler from the MathLive virtual keyboard used innerHTML, letting sandboxed code inject an unsandboxed iframe. A YouTube oEmbed endpoint allowed by the CSP reflected JavaScript, enabling exfiltration of private data via a ChatGPT share URL. OpenAI fixed it and paid a $5,000 bounty.
AppSec, AI Securityยท Published and added 31 Oct 2026



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