Of course they did. No huge body of code is free of flaws. So what? The sky is blue, is that also a revelation?
Your awe at the simplest things make me wonder if you're new to this topic....
That's certainly true.
But the fact remains, Apple apparently still fails to utilize a basic protective capability built into the processors on which it runs by diligent Intel engineers: data execution prevention. DEP keeps many of those undiscovered flaws from having consequences beyond crashing the application you are using at the time.