XSS made easy for testers, developers and managers

Introduction

This may be obvious but XSS is one of my favourite vuleranbility types because of the depth and complexity. It all seems so super simple but when you really get down to the core of XSS there is a world of wonder to explore. Besides the different types of XSS ( Being reflected, stored and DOM — blind XSS is another form of stored XSS ) there are also a lot of different contexts which most people seem to glance over completely. Most courses and articles that cover XSS will only concern themselves with HTML injection but this is just a small part of what XSS is all about.

We will look at what it takes to look for all kinds of XSS attacks in all sorts of contexts but also at what we can do to stop this kind of attack.

What is XSS?

First we need to know why this vulnerability type occurs and we can state that this issue can arise wherever the developer takes user input and renders it onto the page without sanitizing that input. There are several ways to sanitise the input of which the safest but also most restrictive seems to be whitelist based filtering.

Whitelist based filtering is implemented by checking every single piece of user content and only allowing it if that user input is defined on a whitelist. As you can see this can be…