What was the alleged zero-day used? The article fails to mention whether the security researcher used ChatGPT to implement a known zero-day or if it discovered

What was the alleged zero-day used? The article fails to mention whether the security researcher used ChatGPT to implement a known zero-day or if it discovered one on its own. I don't think "AV doesn't detect this malware" qualifies as a zero-day on its own...