Code execution via unsafe checkpoint deserialization

Code injection in NVIDIA Transformers4Rec allows local users to execute arbitrary code through a malicious model checkpoint. The load_model_trainer_states_from_checkpoint function passes t4rec_model_class.pkl to unrestricted cloudpickle.load, permitting pickle reducers to invoke attacker-chosen operations. Exploitation requires an attacker-supplied checkpoint to be loaded; code runs as the target process and gains elevated privileges only when that process is privileged.