Cross-Site Request Forgery (CSRF)

5 minutes 5 Questions

Cross-Site Request Forgery (CSRF) is a web security vulnerability that forces a user's browser to perform unwanted actions on a web application in which they are authenticated. CSRF attacks exploit the trust that web applications have for authenticated users and can result in unauthorized data modification, unauthorized transaction execution, or even account takeover. Defending against CSRF attacks involves implementing proper anti-CSRF tokens, verifying the origin of requests, and following the principle of least privilege.

Guide on Cross-Site Request Forgery (CSRF)

Cross-Site Request Forgery (CSRF) is a type of malicious exploit of a website wherein unauthorized commands are transmitted from a user that the website trusts. It is significant because it breaches trust and privacy by deceiving the website and causing an unsuspecting user to carry out functions.

How CSRF Works:
1. The attacker creates a malicious link containing a command that they wish to force the user to execute.
2. This link is then sent to the user, usually embedded within an innocuous-looking website or an email.
3. If the user clicks on the link while being authenticated on the target site, the command is silently executed using the user's credentials.
4. The website can't distinguish between a legitimate request from the user and a forged request.

Exam Tips - Answering Questions on Cross-Site Request Forgery (CSRF):
While answering exam questions related to CSRF, keep in mind that you need to:
- Understand the basic mechanics of CSRF attacks.
- Know the prevention methods, such as using anti-CSRF tokens or Same Site Cookies.
- Be able to explain how it's different from Cross-Site Scripting (XSS), as XSS involves injecting malicious code into websites, while CSRF involves tricking the client into executing a command that benefits the attacker.

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Question 1

A company has implemented a password reset form that includes a secret question and answer as part of the process. An attacker can reset a victim's password by submitting a CSRF attack with a forged password reset request. What method can the developer use to prevent this attack?

Limit the number of password resets per day Implement a CSRF token check Use the user's IP address to check the validity of the request Enable a user agent-based check

Correct Answer: Implement a CSRF token check

Implementing a CSRF token check prevents attackers from forging requests by requiring a valid token for each request. Limiting the number of password resets, checking the IP address or user agent, hashing the secret question and answer, or decreasing session timeout do not address the CSRF vulnerability directly.

Question 2

An e-commerce website allows users to view their order history. After logging in, a user can access the order history page by clicking the "viewOrder?id=xxx" link. An attacker sends a victim an email with an image element pointing to the "viewOrder?id=yyy" URL. How can the developer mitigate this potential CSRF attack?

Create a random number generator Implement SameSite attribute to cookies Clear the user's browser cache Improve the website's user interface

Correct Answer: Implement SameSite attribute to cookies

By setting the SameSite attribute to cookies, the server can inform the browser to prevent cookies from being used across different domains. Improving the website UI, creating a random number generator, clearing the cache, using rate limiting, and utilizing a firewall do not directly mitigate CSRF in this scenario.

Question 3

A social media website's "like" feature uses a link in the following format: "like.php?post_id=123456". An attacker sends a link to the victim's email with the same URL format to trick the user into liking a malicious post. What measure can the developer implement to prevent abuse of this "like" feature?

Use AJAX instead of a link Add a CSRF token to the URL Switch to HTTP GET Implement JavaScript validation

Correct Answer: Add a CSRF token to the URL

Adding a CSRF token to the URL allows the server to verify the authenticity of the request and makes it difficult for an attacker to forge requests. Using AJAX, JavaScript validation, changing the URL structure, or increasing the session timeout do not mitigate the CSRF attack in this scenario. Switching to HTTP GET is incorrect since the "like" feature is already using the GET method.

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