See https://makandracards.com/makandra/620779-rails-require-permit-attributes for a rewrite of this topic
Rails 4:
config.action_controller.action_on_unpermitted_parameters enables logging or raising an exception if parameters that are not explicitly permitted are found. Set to :log or :raise to enable. The default value is :log in development and test environments, and false in all other environments.
Rails 3:
If you include the strong_params gem, see 
  the Readme
  
    Show archive.org snapshot
  
 for handling unpermitted keys.
Posted to makandra dev (2014-05-12 08:46)