The things under Web Security are the relevant bits. You can read up on a lot of them at https://www.owasp.org/index.php/Main_Page and I'd recommend just googling them as well. More importantly, grab Burp proxy, install old (vulnerable) versions of web apps, and start playing around. You'll find XSS, SQLi, and plenty of other fun things in no time.
Also, my contact info is in my profile if you have other questions.