ether.fi lost approximately 15.45 ETH after an access-control vulnerability in its AtomicQueue contract was exploited. The flaw in the solve() function allowed an attacker to use updateAtomicRequest() to create a malicious request and designate a victim address as the solver. AtomicQueue then called the victim’s finishSolve function and executed want.transferFrom, abusing the victim’s existing ERC-20 allowance to transfer funds. SlowMist privately disclosed the issue to ether.fi before publishing the attacker address and vulnerable contract address.