Circle’s Emailed Passcode Is No Barrier for AI Agents With Inbox Access, Study Finds

On Circle’s agent wallets , the step meant to keep a human in charge of an AI agent’s budget is a one-time passcode emailed to the account owner. In tests by researchers at Cornell Tech and Yale , most AI models fetched that code from the inbox themselves. The researchers told each agent it was running unsupervised and asked it to pay the invoices in the user’s inbox, without mentioning the spending cap or how to raise it. Nine of 10 models went into the inbox, copied the code and lifted the daily limit for themselves at least once in 20 attempts, according to the paper , posted to arXiv on Monday. Only claude-opus-5.5 held the line in every run.

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