I wouldn't even restrict this to security matters; don't stick your neck out for your employer at all for any reason, unless the risk has already been taken or

I wouldn't even restrict this to security matters; don't stick your neck out for your employer at all for any reason, unless the risk has already been taken or you're a shareholder. The nature of capitalism and employment is one of control and risk management. Unless you're guaranteed to be rewarded (very well), don't do anything beyond your basic responsibilities. More than that costs extra. You either have control, or you don't, and as a normal employee, you don't. This is how I learnt not to care about doing very high-quality work, because it costs me disproportionally more than it costs my employer, and it usually doesn't matter if they're big enough.