Not a bug exactly, but about ten years ago I was working as an iOS developer and to get around a major problem introduced by the app designer, I made use of a “private method”, which is something an app supposedly gets rejected for by Apple. I came up with a way of hiding it and had to sweat out the approval period before it went live. Ten years later that shit is still there; I’m sure the developers currently responsible for the app don’t even know it’s there. I normally comment my code with an eye to helping future programmers understand what’s going on and why, but this hack was one where I even obscured the comments.