Details on the strategy employed by the human are at https://goattack.far.ai:

We discovered simple adversarial strategies that beat superhuman Go AIs, and find that adding defenses helps but does not eliminate the problem. Our cyclic adversary beats the state-of-the-art KataGo AI more than 97% of the time at superhuman settings. This strategy is simple enough to be replicated by an amateur human player and transfers to other superhuman Go AIs.