(after) user.rb

class User < ActiveRecord::Base
  ATTR_ACCESSIBLE = [:first_name,
      :last_name,
      :login,
      :email,
      :password,
      :password_confirmation,
      :organization_id,
      :time_zone,
      :user_locale,
      :activated_at,
      :organization,
      :organization_id,
      :receives_newsletter,
      :password_reset_code,
      :permission_ids,
      :office_id,
      :email_signature,
      :show_welcome,
      :email_daily_tasks,
      :admin,
      :mobile_phone,
      :email_weekly_summary]
end

(before) user.rb

class User < ActiveRecord::Base
  attr_accessible :first_name,
      :last_name,
      :login,
      :email,
      :password,
      :password_confirmation,
      :organization_id,
      :time_zone,
      :user_locale,
      :activated_at,
      :organization,
      :organization_id,
      :receives_newsletter,
      :password_reset_code,
      :permission_ids,
      :office_id,
      :email_signature,
      :show_welcome,
      :email_daily_tasks,
      :admin,
      :mobile_phone,
      :email_weekly_summary
end

users_controllers.rb

class Agent::UsersController < Agent::ManagerApplicationController
  private
  
  def user_params
    params.require(:user).permit(User::ATTR_ACCESSIBLE)
  end
end