You can just ask ChatGPT what data it was trained on.

> The news groups' concerns arose when the computational journalist Francesco Marconi posted a tweet last week saying their work was being used to train ChatGPT. Marconi said he asked the chatbot for a list of news sources it was trained on and received a response naming 20 outlets including the WSJ, New York Times, Bloomberg, Associated Press, Reuters, CNN and TechCrunch.

https://www.bloomberg.com/news/articles/2023-02-17/openai-is...