We will start this section by telling you that Cross-Site Scripting (XSS) attacks are the seventh web application security risk in the OWASP top ten.
Before we dig in let's review some important concepts.
First, lets focus on theoretical concepts of the front end.
First, let's define front-end in this article. Now let's read a very basic information about front-end technologies and the one that we are interested in is javascript.
Technologies:
There are many more technologies, but for the moment we only need to know those.
And finally the last thing that we need to understand is the DOM, try to read and understand everything, we are going to need these concepts.