A lot of vulnerabilities are rather obvious, but hard to avoid due to more than one person working on a project. For a sufficiently large project it's not alwa

A lot of vulnerabilities are rather obvious, but hard to avoid due to more than one person working on a project. For a sufficiently large project it's not always obvious that another implementation of something exists. And it's not always easy to search for a concept. You might use different words for it than the other person that implemented it. And even if you find it, it might have a weird badly thought out API and similar implementation, making it likely people reimplement it anyway.