You'd be surprised what programmers will do. Sometimes due to incompetence, sometimes it's an "optimization", sometimes it's a simple mistake, yet there is some

You'd be surprised what programmers will do. Sometimes due to incompetence, sometimes it's an "optimization", sometimes it's a simple mistake, yet there is some very bad code out there and it's not discovered until it causes a problem. For example, even a newbie wouldn't trust a remote client to tell you the size of a string they are sending you so you can echo it back to them, yet we still had Heartbleed and it sat there for a long time, undiscovered.