Quick definition: Cross-Site Request Forgery (CSRF) is an attack that tricks a logged-in user into executing unwanted actions on a web application. it exploits the trust a site has in the user’s browser.
Explanation
Cross-Site Request Forgery (CSRF), also known as XSRF or “sea surf,” is a web security vulnerability that tricks a user’s browser into performing unauthorized actions on a trusted website where the user is currently authenticated. This attack exploits the inherent trust a web application has in a user’s browser, which automatically includes credentials like session cookies or IP addresses with every request. By using social engineering, such as malicious links in emails or hidden scripts on compromised pages, an attacker can force state-changing actions like transferring funds, changing account passwords, or updating personal information without the user’s knowledge.
A common misconception is that CSRF allows an attacker to steal data directly; however, it is primarily used to execute actions rather than retrieve information, as the attacker cannot see the server’s response. Another myth is that only using POST requests instead of GET requests provides sufficient protection. In reality, attackers can easily bypass this using JavaScript to submit forged forms. Modern defenses include the use of unique anti-CSRF tokens and SameSite cookie attributes to ensure requests originate from a legitimate source.
Why it matters
- – Helps prevent unauthorized actions on your accounts, such as transferring funds or changing passwords, by ensuring that only requests you intentionally initiate are processed
- – Reduces the risk of identity theft and account takeover by requiring websites to verify that a request truly came from you and not a malicious third-party site
- – Encourages safer browsing habits, like logging out of sensitive accounts when finished, which adds a simple but effective layer of protection against background exploits
How to check or fix
- – Implement unique, cryptographically strong anti-forgery tokens for all state-changing requests, such as POST, PUT, and DELETE
- – Configure session cookies with the SameSite attribute set to Strict or Lax to prevent them from being sent during cross-site requests
- – Verify the source of requests by checking the Origin and Referer HTTP headers to ensure they match your expected domain
- – Require users to re-authenticate or solve a CAPTCHA before performing sensitive actions like changing passwords or transferring funds
- – Ensure that GET requests are only used for retrieving information and do not trigger any side effects or changes to the application state
- – Use custom HTTP headers for AJAX and API requests, as browsers typically restrict the addition of these headers in cross-origin contexts
Related terms
Cross-Site Scripting (XSS), Anti-CSRF Token, Same-Origin Policy, Session Cookie, Social Engineering, SameSite Cookie Attribute
FAQ
Q: What is Cross-Site Request Forgery (CSRF)?
A: CSRF is a cyber attack that tricks an authenticated user into submitting malicious requests to a web application without their knowledge.
Q: How can a website prevent CSRF attacks?
A: Developers can mitigate these attacks by using unpredictable CSRF tokens, enforcing SameSite cookie attributes, and validating Origin or Referer headers.
Q: What is a CSRF token?
A: A CSRF token is a unique, secret value generated by the server and shared with the client to verify that a state-changing request is legitimate and intentional.