In our profession, it's common to work on an unfamiliar codebase. It happens every time one joins a new project or even needs to work on a previously untouched part in big ones. This occurrence is not limited to a developer having to fix a bug; it can be a solution architect having to design a new feature or an OpenSource contributor working on a GitHub issue in their free time. Hence, I want to describe how I approach the situation so it can benefit others.
An Example Issue
To illustrate my point, I'll use a common GitHub issue requesting a new feature on an Open Source project.