For the record, I'm not the one downvoting you (I don't even have that ability yet!). Security is always done in layers, though, and while you're correct that

For the record, I'm not the one downvoting you (I don't even have that ability yet!). Security is always done in layers, though, and while you're correct that it is extremely unlikely, the chance is nonzero. As such you have to prepare for that and design your system to be resilient to these types of things. In castle terms, you trust that no one will ever breach your wall, but that doesn't mean you don't have guards and an armory inside for the unlikely event it does.