“Hacking” AI with only words.

Groups of people on the internet start sharing techniques and strategies for getting AI to give you the best deal on flights, cars, whatever.

Using only word prompts, some people get extremely good at this, occasionally getting products and services for free.

Phrases include ideas of self-harm, harming the AI or the business, threats to slander the company, etc. Occasionally, a string of nonsensical words get the desired outcome.

Would this be a form of hacking, and therefore be illegal?

Could the threats be considered legitimate, even though they are understood to be not real?