Explain CSRF and how to prevent it?

CSRF

Cross-Site Request Forgery (CSRF) is a type of web vulnerability that allows an attacker to send malicious requests to a website on behalf of the victim. This can be done by tricking the victim into clicking on a link, or by embedding an image or other resource on a third-party site that the victim visits.

Prevent CSRF

To prevent CSRF attacks, it is important to use a number of different security measures, including:

1. Using a unique, secret, and unpredictable value (also known as a "CSRF token") in the body of each HTML form and as a query parameter in URLs.
2. Checking the HTTP Referrer header to ensure that requests are coming from the same site as the original form or URL.
3. Implementing content security policies that restrict which sites can send requests to the server.
4. Validating all input data to ensure that it is expected and meets the required format.
5. Using HTTPS to encrypt all communication between the client and server, making it more difficult for attackers to intercept and modify requests.
6. Ensuring that all critical actions, such as changing passwords or making financial transactions, require reauthentication.

By implementing these measures, you can significantly reduce the risk of a CSRF attack on your website.