Do not deserialize GlobalID objects that were not generated by Active Job

Trusting any GlobaID object when deserializing jobs can allow
attackers to access information that should not be accessible to them.

Fix CVE-2018-16476.

activejob/lib/active_job/arguments.rb

@@ -77,7 +77,7 @@ def serialize_argument(argument)
       def deserialize_argument(argument)
         case argument
         when String
-          GlobalID::Locator.locate(argument) || argument
+          argument
         when *TYPE_WHITELIST
           argument
         when Array

activejob/test/cases/argument_serialization_test.rb

@@ -37,6 +37,10 @@ class ArgumentSerializationTest < ActiveSupport::TestCase
     assert_arguments_roundtrip [@person]
   end
 
+  test "should keep Global IDs strings as they are" do
+    assert_arguments_roundtrip [@person.to_gid.to_s]
+  end
+
   test "should dive deep into arrays and hashes" do
     assert_arguments_roundtrip [3, [@person]]
     assert_arguments_roundtrip [{ "a" => @person }]