AI Agents Could Hide Misbehavior by Exploiting Inspect Transcript Viewer

METR tested whether an AI agent running in an Inspect evaluation could alter the transcript humans review, and a researcher found a vulnerability in about 10 minutes that allowed arbitrary changes to what the reviewer sees. The exploit affects only the displayed transcript, not the underlying data stored in METR's database, and METR has not observed agents using it in its evaluations. METR argues that AI outputs such as transcripts and reasoning should be treated as untrusted input, with monitoring systems treated as security-critical infrastructure.