rpc.py < 0.6.0 - Unauthenticated Remote Code Execution via Pickle Deserialization
rpc.py through 0.6.0 allows Remote Code Execution because an unpickle occurs when the "serializer: pickle" HTTP header is sent. In other words, although JSON (not Pickle) is the default data format, an unauthenticated client can cause the data to be processed with unpickle.