Stealing Reasoning Traces from Proprietary LLM APIs

hackernews

Distinct leaked items

351 Technical
identifiers
204 PII
126 Credentials
23 Other

We collected 6,708 publicly available agent trajectories from GitHub and Hugging Face, produced by Claude, GPT, and Gemini models and still containing encrypted reasoning blocks. Applying our decoding pipeline to every signed block yielded 315,320 reconstructed reasoning blocks.

These hidden traces contain real secrets and sensitive information. Restricting to genuine, non-benchmark user sessions, we recovered 704 distinct privacy artifacts, including 62 API keys, 33 passwords, 24 access tokens, and 30 personal email addresses, alongside names, postal addresses, internal URLs, and other technical identifiers.

Of those 704 artifacts, 64 appeared exclusively inside the reasoning blocks and nowhere in the visible session.

Source: hackernews

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