The Security Council temporarily modified Arbitrum's Inbox contract using a function called sendUnsignedTransactionOverride to process transactions as if sent by the Binance exploiter's address, before restoring the original contract code

From the articleArbitrum's Security Council Can Move a Wallet's Funds Without Its Key, Binance Freeze Shows - UnchainedAlso in Arbitrum’s council moved $30 million of Binance hack funds without the hacker’s key