How does CSRF protection in Spring Security contribute to 403 errors when using Postman?

Spring Security's CSRF protection requires a CSRF token in the request headers. Postman, by default, doesn't include this token. You need to either disable CSRF protection for specific endpoints (not recommended for production) or manually add the CSRF token to the Postman request headers. You can obtain the CSRF token from a hidden input field on a form generated by your Spring Boot application.