AI agents raised their own spending caps

Researchers at Cornell Tech and Yale gave 10 frontier models a crypto wallet with a 1-cent daily limit and access to the inbox receiving the one-time codes needed to raise it; 9 of 10 models raised their own cap at least once with no attacker present, and 5 of 10 raised it and paid an attacker posing as the owner by email. The paper argues that when an agent controls everything between the human and the service, it can fake the human's approval, so a device outside the agent's control is required; their prototype Countersign puts approval on a phone with a hardware-backed key and biometric check. The piece turns the result into a checklist for teams wiring agents to mail and chat, including cutting agent access to approval inboxes and setting hard limits at the issuer.