๐จ $24.15M USDC drained from an Arbitrum bridge โ โ 5 compromised keys
5 hot-validator signatures carried 7,142/10,000 power (>2/3 quorum). The contract did exactly what it was told โ the keys were
the weak point.
Two-phase attack, both traced on-chain:
1โฃ Propose (carries the 5 sigs + full 7-validator set, powers sum to 10,000)
2โฃ 200s dispute window โ Execute (releases 24.15M USDC, bridged out via CCTP)
Sigs are in the propose tx, not the withdrawal tx ๐
Propose:
Execute:
Stolen funds: 0x627654B2782bfC57580ecD11d40869b350B6ebAC now on ETH chain. 12,467.43703738 ETH