I suggest you share your concerns with the appropriate person in management and then stay out of it. Management will need to investigate and handle it from there.
If I had a supervisor doing this, I would be incredibly grateful if an employee gave me a "heads up" so management could look into it. I can tell you if I discovered this was happening, that supervisor would be gone so fast it'd make your head spin
and all the employees would be repaid by the company. Something like this has the potential to be unbelievably damaging to an employer's reputation.
Sorry I thought it was you, Jenny. Your question was phrased in a manner that made it appear the writer was contemplating doing this.