Can an market EA be a scam?

[Camilo Mora]

I recently noted an EA with some amazing performance even in my own backstesting of it (a 98% accuracy, a 49 profit factor).  The user interface is pretty simple and very few parameters one can modify other than the number of entries and how big they can be. It can only operate one pair. Of course, with such a few parameters to enter, the EA always enters at the same times, with different volumes.

We all know that one can super-overfit an EA, such that always performs well on the backtesting but the one thought that struck me is...can one simply create an EA with set times to enter, and let the user just modify how big the entries?

Are there any general recommendations about the homework one needs to do before purchasing an EA?

I see some obvious things to do like doing the backtest, which given the above considerations, if true, could be fooled, looking at the reviews, if any; any other....