ether.fi disclosed that a legacy withdrawal queue was abused to drain about 15.45 ETH from a small set of wallets that still had old approvals in place. The issue did not affect the protocol’s core minting or vault accounting, but it did expose the danger of deprecated contracts that remain callable after they should have been retired.
The weakness was an authorization failure in the queue’s settlement flow. A contract design that accepts a caller-supplied role or address without verifying consent creates a path for attackers to redirect approved token transfers through a legitimate-looking settlement process.
This is a reusable smart contract risk because it combines stale permissions, outdated contract logic, and insufficient access control. Any protocol that leaves old approvals active on legacy contracts can become vulnerable even if its main contracts are sound.
Defenders should minimize long-lived approvals, add explicit signature-based consent for settlement actions, and permanently disable or isolate deprecated helpers. User-facing tooling should also warn about stale allowances and make revocation easy before old contracts are exploited.