Cross Site Scripting and SQL injection explained

OWASP has a full range of videos that give you a basic view of XSS and SQL injection:

SQL injection

Full table and column traversal and site take-over is almost an inevitable consequence of non-managed user input and system output (like error messages). This OWASP video gives you a quick introduction.

Cross Site Scripting (XSS)

Easy to exploit, easy to find, highly varied – script injection in Javascript, typically to attack other users and exploit them.

You can find out more in the AppSec Tutorial Series by OWASP