I would like to know anyone’s opinion on this.

Recent work has identified that classification models implemented as neural networks are vulnerable to data-poisoning and Trojan attacks at training time.

Source: Attacks on Deep Reinforcement Learning Agents : https://arxiv.org/abs/1903.06638

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1. Is it a real threat?
2. How the risk can be identified from someone that just uses the model without access to its source or training data (i.e. prepare a set of tests)?