1 files changed, 20 insertions, 7 deletions
diff --git a/activemodel/lib/active_model/forbidden_attributes_protection.rb b/activemodel/lib/active_model/forbidden_attributes_protection.rb
index a5e4c4f650..4c05b19cba 100644
--- a/activemodel/lib/active_model/forbidden_attributes_protection.rb
+++ b/activemodel/lib/active_model/forbidden_attributes_protection.rb
@@ -1,14 +1,27 @@
 module ActiveModel
+  # Raised when forbidden attributes are used for mass assignment.
+  #
+  #   class Person < ActiveRecord::Base
+  #   end
+  #
+  #   params = ActionController::Parameters.new(name: 'Bob')
+  #   Person.new(params)
+  #   # => ActiveModel::ForbiddenAttributesError
+  #
+  #   params.permit!
+  #   Person.new(params)
+  #   # => #<Person id: nil, name: "Bob">
   class ForbiddenAttributesError < StandardError
   end
 
-  module ForbiddenAttributesProtection
-    def sanitize_for_mass_assignment(attributes, options = {})
-      if attributes.respond_to?(:permitted?) && !attributes.permitted?
-        raise ActiveModel::ForbiddenAttributesError
-      else
-        attributes
+  module ForbiddenAttributesProtection # :nodoc:
+    protected
+      def sanitize_for_mass_assignment(attributes, options = {})
+        if attributes.respond_to?(:permitted?) && !attributes.permitted?
+          raise ActiveModel::ForbiddenAttributesError
+        else
+          attributes
+        end
       end
-    end
   end
 end