Lab: CSRF where token is duplicated in cookie
This lab's email change functionality is vulnerable to CSRF. It attempts to use the insecure "double submit" CSRF prevention technique.
To solve the lab, use your exploit server to host an HTML page that uses a CSRF attack to change the viewer's email address.
You can log in to your own account using the following credentials:
- With your browser proxying traffic through Burp Suite, log in to your account, submit the "Update email" form, and find the resulting request in your Proxy history.
Send the request to Burp Repeater and observe that the value of the
csrfbody parameter is simply being validated by comparing it with the
- Perform a search, send the resulting request to Burp Repeater, and observe that the search term gets reflected in the Set-Cookie header. Since the search function has no CSRF protection, you can use this to inject cookies into the victim user's browser.
Create a URL that uses this vulnerability to inject a fake
csrfcookie into the victim's browser:
- Create and host a proof of concept exploit as described in the solution to the CSRF vulnerability with no defenses lab, ensuring that your CSRF token is set to "fake". The exploit should be created from the email change request.
Remove the script block, and instead add the following code to inject the cookie and submit the form:
<img src="$cookie-injection-url" onerror="document.forms.submit();"/>