How Parameter Labs Used ChatGPT HTML Previews to Access Private Account Data
Parameter Labs found an exploit chain that let a ChatGPT share URL exfiltrate private data or take actions on behalf of another signed-in user who visited it, Simon Willison reports. The attack combined MathLive message handling, HTML injection, an unsandboxed iframe, and YouTube’s oEmbed endpoint to execute JavaScript despite OpenAI’s CSP restrictions. OpenAI fixed the vulnerability and paid a $5,000 bug bounty, which Willison considers low for its severity.
Why it matters
The exploit illustrates how a sandboxed HTML preview could reach private account data through weaknesses spanning message handling, HTML injection, and permitted script sources.










