Copy validators lists on instantiation.

rest_framework/serializers.py

@@ -327,7 +327,9 @@ class Serializer(BaseSerializer):
         Returns a list of validator callables.
         """
         # Used by the lazily-evaluated `validators` property.
-        return getattr(getattr(self, 'Meta', None), 'validators', [])
+        meta = getattr(self, 'Meta', None)
+        validators = getattr(meta, 'validators', None)
+        return validators[:] if validators else []
 
     def get_initial(self):
         if hasattr(self, 'initial_data'):
@@ -1213,7 +1215,7 @@ class ModelSerializer(Serializer):
         # If the validators have been declared explicitly then use that.
         validators = getattr(getattr(self, 'Meta', None), 'validators', None)
         if validators is not None:
-            return validators
+            return validators[:]
 
         # Otherwise use the default set of validators.
         return (