3 files changed, 27 insertions, 6 deletions
diff --git a/actionpack/lib/action_controller/metal.rb b/actionpack/lib/action_controller/metal.rb
index 8e040bb465..f6a93a8940 100644
--- a/actionpack/lib/action_controller/metal.rb
+++ b/actionpack/lib/action_controller/metal.rb
@@ -166,7 +166,7 @@ module ActionController
 
     alias :response_code :status # :nodoc:
 
-    # Basic url_for that can be overridden for more robust functionality
+    # Basic url_for that can be overridden for more robust functionality.
     def url_for(string)
       string
     end
diff --git a/actionpack/lib/action_controller/metal/redirecting.rb b/actionpack/lib/action_controller/metal/redirecting.rb
index aeecb48f85..b13ba06962 100644
--- a/actionpack/lib/action_controller/metal/redirecting.rb
+++ b/actionpack/lib/action_controller/metal/redirecting.rb
@@ -60,7 +60,6 @@ module ActionController
     #
     def redirect_to(options = {}, response_status = {}) #:doc:
       raise ActionControllerError.new("Cannot redirect to nil!") unless options
-      raise ActionControllerError.new("Cannot redirect to a parameter hash!") if options.is_a?(ActionController::Parameters)
       raise AbstractController::DoubleRenderError if response_body
 
       self.status        = _extract_redirect_to_status(options, response_status)
@@ -68,8 +67,14 @@ module ActionController
       self.response_body = "<html><body>You are being <a href=\"#{ERB::Util.unwrapped_html_escape(location)}\">redirected</a>.</body></html>"
     end
 
-    # Redirects the browser to the page that issued the request if possible,
-    # otherwise redirects to provided default fallback location.
+    # Redirects the browser to the page that issued the request (the referrer)
+    # if possible, otherwise redirects to the provided default fallback
+    # location.
+    #
+    # The referrer information is pulled from the HTTP `Referer` (sic) header on
+    # the request. This is an optional header and its presence on the request is
+    # subject to browser security settings and user preferences. If the request
+    # is missing this header, the <tt>fallback_location</tt> will be used.
     #
     #   redirect_back fallback_location: { action: "show", id: 5 }
     #   redirect_back fallback_location: post
diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index 8bc3c271e2..957aa746c0 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -1,4 +1,5 @@
 require 'active_support/core_ext/hash/indifferent_access'
+require 'active_support/core_ext/hash/transform_values'
 require 'active_support/core_ext/array/wrap'
 require 'active_support/core_ext/string/filters'
 require 'active_support/rescuable'
@@ -175,7 +176,7 @@ module ActionController
     #   safe_params.to_h # => {"name"=>"Senjougahara Hitagi"}
     def to_h
       if permitted?
-        @parameters.deep_dup
+        convert_parameters_to_hashes(@parameters)
       else
         slice(*self.class.always_permitted_parameters).permit!.to_h
       end
@@ -185,7 +186,7 @@ module ActionController
     # <tt>ActiveSupport::HashWithIndifferentAccess</tt> representation of this
     # parameter.
     def to_unsafe_h
-      @parameters.deep_dup
+      convert_parameters_to_hashes(@parameters)
     end
     alias_method :to_unsafe_hash, :to_unsafe_h
 
@@ -594,6 +595,21 @@ module ActionController
         end
       end
 
+      def convert_parameters_to_hashes(value)
+        case value
+        when Array
+          value.map { |v| convert_parameters_to_hashes(v) }
+        when Hash
+          value.transform_values do |v|
+            convert_parameters_to_hashes(v)
+          end.with_indifferent_access
+        when Parameters
+          value.to_h
+        else
+          value
+        end
+      end
+
       def convert_hashes_to_parameters(key, value)
         converted = convert_value_to_parameters(value)
         @parameters[key] = converted unless converted.equal?(value)