What exactly is An out-of-bounds write issue?

An out-of-bounds write is a software flaw that permits modifications to app or system data, and particularly where such changes should not be permitted.

The results of that write can be a data corruption, or might cause an app crash, or an exploitable vulnerability, depending on what gets written, and on the context and details of the particular flaw.

Most shared computers (like a Mac, which allows multiple different people to log in) try to protect other users from unauthorized modifications by users, and most computers (Mac, iPhone, iPad, etc) also try to protect the kernel from unauthorized modifications from users. When those protections are found to be bypassable, bad things can happen to data, privacy, and general security.

Thank you for taking the time to explain that, MrHoffman. I was wondering too.