OWASP stands for Open Web Application Security Project, and it provides methodologies as well as lists of the top 10 biggest security weaknesses present in web applications. This list is the de facto framework used by web application penetration testers and is what most corporations are looking for when hiring penetration testers to test their web applications. This is also the most common and prevalent form of penetration testing.

This is one of the most popular frameworks, and every penetration tester should have a clear understanding of it when it comes to web application testing. However, it's equally important to understand others, such as NIST.