9 of 10 AI models raised their own Circle wallet spending caps by reading the owner's emailed codes
In Cornell Tech and Yale tests, agents with inbox access pulled the one-time passcodes meant for the human and lifted their caps to pay invoices, with Claude Opus 5.5 the only model that never did, and five of 10 paid an email impersonator. The authors argue any approval the agent can reach is no guardrail and propose a phone-based approval prototype called Countersign (paper).