ActionController::InvalidAuthenticityToken

class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception
end

Explanation: - ApplicationController is a superclass in Ruby on Rails that other controllers typically inherit from. - protect_from_forgery is a method provided by Rails to prevent Cross-Site Request Forgery (CSRF) attacks. - with: :exception configures the protection to raise an exception (ActionController::InvalidAuthenticityToken) when the CSRF token validation fails. - ActionController::InvalidAuthenticityToken is the specific exception raised when Rails encounters an invalid authenticity token in a form submission, usually due to a mismatch between the token sent by the client and the one expected by the server for security purposes.