Prerequisites:

  • Have basic knowledge of the web
  • Definition

    The XSS vulnerability is a client-side web vulnerability, ranked in the top 10 of the OWASP ranking. It is a vulnerability consisting in injecting JavaScript code into a web page. This vulnerability allows for example to modify the behavior of a page or the theft of cookies among others … We can distinguish three types of XSS:

  • Stored XSS
  • Reflected XSS
  • DOM Based XSS
  • Introduction to the 3 types of XSS

    In this part I will give you a short introduction to each type of XSS, for more details, see my other articles on the subject.

    Stored XSS

    Stored XSS is a type of XSS where the injected script is stored in the database and displayed to other users. For example a forum page. This type of XSS can be very dangerous because as long as the database is not changed, all users will be attacked. Regarding the exploit, it is a classic exploit with <script> tags.

    Reflected XSS

    XSS is considered reflected when the malicious script is in a parameter of the url. Like for example a function “Search” which would have a parameter “?search=xss”. The advantage of this XSS is to be able to target a user in particular by sending him our trapped url. As for the stored XSS it is a classic exploit.

    DOM Based XSS

    This type of XSS is a bit special because it does not require server intervention. This XSS is possible when user input is found directly in the JavaScript code, which therefore allows us to modify the JavaScript code instead of adding it as we did with other XSS. Like for example a game page coded in Javascript where you have to find a random number. The exploit is different than the 2 others because it does not require tags since we act directly on the code.