It doesn't matter if it is Windows, Mac, iOS, Android, or Linux, all software is full of bugs.
For that matter, all of everything constructed by human beings...is full of defects, or potential defects, or security vulnerabilities. Your house, for example. You have a lock on your front door, but it takes a thief just a few seconds to kick the door in. Or your car...a thief can break into it in seconds, even if you have electronic theft protection. I'd call those "security vulnerabilities."
It's the nature of all human creations, software or hardware, electronic or mechanical.
So what do we do? We improve security until it becomes "just secure enough" that we can live with the risks, and move on.