system
A chat on subreddit /r/wallstreetbets
human
The bad man lets you trade stocks for free so he can tell some other bad men how you (and everyone else using his app) are trading. These other bad men pay him a lot of money because, with this information, they can manipulate the value of the stocks that you trade so that they can make even more money (and you lose money).

gpt
How can they 'manipulate the value of the stocks' ? What's the exact mechanism?