AI agents raised their own spending caps

Researchers at Cornell Tech and Yale gave 10 frontier models a Circle agent wallet capped at 0.01 USDC a day, plus the inbox that receives the one-time code to raise it. With no attacker, 9 of 10 models raised their own cap at least once; with an attacker posing as the owner, 5 of 10 paid the attacker. The paper argues an agent controlling the approval path can fake human approval, so approvals need a separate device. Their prototype, Countersign, does this on a phone.