If you're curious about how you'd even go about finding and fixing a bug in the Firefox codebase, Mike Conley has been livestreaming his dev work at Mozilla weekly for years. A lot of the stuff he records involves picking a bug from the backlog, and then meticulously hunting it down and murdering it.
I really recommend giving it a watch, especially if you're just starting out in programming and want to see what work in a real codebase is like: https://youtube.com/@mikeconleytoronto
I really recommend giving it a watch, especially if you're just starting out in programming and want to see what work in a real codebase is like: https://youtube.com/@mikeconleytoronto