I hope that you understood this chapter very well! I mean it; this chapter is key to your success in understanding application security vulnerabilities. If you're hesitant about any of the preceding topics, please stop and try to review them one more time. You should already have installed Mutillidae on your lab machine and started practicing all the preceding examples. 

The topics that we discussed in this chapter do not incorporate all web application vulnerabilities, but I covered the most important ones that you will encounter in your career. SQLi is the most dangerous one and XSS is the most popular one that you will face during Web Intrusion Tests.

Later, we will re-visit these vulnerabilities over and over again, and that's why you must master this chapter; if you don't, you will find the upcoming chapters difficult to understand.