Not exactly clients, but the Parity multisig "hack"[0] was pretty wild. All it took was one permissionless call to permanently wipe the shared library of a larg

Not exactly clients, but the Parity multisig "hack"[0] was pretty wild. All it took was one permissionless call to permanently wipe the shared library of a large bunch of multisig wallets, thereby freezing those wallets forever. Some of the impacted people, including Parity, are still pushing for overriding the wallets to be unlocked, despite no support from anyone else. 0: https://blog.zeppelin.solutions/on-the-parity-wallet-multisig-hack-405a8c12e8f7 https://blog.zeppelin.solutions/on-the-parity-wallet-multisi...