XSS

XSS is a vulnerability in a website that allows an attacker to inject client-side scripts into web pages viewed by other clients. A common target for this attack is user session cookies.

Types

Non-persistent (reflected) XSS vulnerabilities simply take user input (e.g. via a form query parameter) and uses it as part of the HTML body or other form of evaluation. The attacker can craft a URL containing the attack and send it to the victim.

Persistent (stored) XSS vulnerabilities are more complex in nature because the attacker must get the server to store malicious data and serve it to users as part of the normal HTML page.

Resources

• Generally, getting a page to execute alert(document.domain) is a sign there is a XSS vulnerability.
  • This can be done within <script> tags or via <img src="javascript:alert(document.domain)">
• https://webhook.site/ can be used to view requests in an attack.