Cross-Site Request Forgery (CSRF) is a type of security vulnerability that occurs when a malicious website tricks a user’s browser into making an unwanted request to a different site on which the user is authenticated. This can lead to actions being performed on the target site without the user’s knowledge or consent.
How about a super simplified example to illustrate how CSRF works:
- User Authentication: Imagine a user logs into their online banking account, and a session cookie is stored in their browser to keep them logged in.
- Malicious Website: The user visits a malicious website (e.g., a forum, an email with hidden content, etc.). This website has a hidden form that submits a request to the bank’s transfer page.
- Hidden Form Submission: When the user visits the malicious site, a form on that page might automatically submit a request to the bank’s transfer page in the background. Since the user is authenticated with the bank, the request is considered valid.
- Unauthorized Action: The bank’s server receives the request and processes it. In this case, it might transfer money to an account controlled by the attacker.
- Result: The user, unaware of the attack, might see funds missing from their account without knowing why.
To mitigate CSRF attacks, web developers can implement several strategies:
- Use Anti-CSRF Tokens: Include unique tokens in forms that are tied to the user’s session. This token must be submitted along with the form and checked on the server to validate the request.
- Check the Origin or Referrer Header: The server can verify that requests are coming from the same domain. However, this method can be bypassed in certain scenarios, so it’s not foolproof.
- Implement SameSite Cookies: Set the SameSite attribute on cookies to restrict when they are sent. This can help prevent cookies from being sent in cross-origin requests.
- Use POST Requests for Sensitive Actions: Sensitive actions like transfers, password changes, etc., should only be allowed via POST requests.
- Educate Users: Users should be aware of the risks of clicking on links from untrusted sources, and they should always log out of sensitive accounts when done using them.
It’s important for both developers and users to be aware of CSRF attacks and how to protect against them. Additionally, web browsers and frameworks often provide built-in protections against CSRF, but developers still need to implement proper security measures in their applications.