Is that simple mistake cost $32 millions in recent Parity hack
https://github.com/paritytech/parity/commit/b640df8fbb964da7538eef268dffc125b081a82f
Looks like initWallet was public and anybody could execute it and here hacker in action
https://etherscan.io/tx/0xff261a49c61861884d0509dac46ed67577a7d48cb73c2f51f149c0bf96b29660 ( calling init )
https://etherscan.io/tx/0x0e0d16475d2ac6a4802437a35a21776e5c9b681a77fef1693b0badbb6afdb083 ( executing )
Naaa.. we dont need to test that, its only an O-Ring