Exploiters can do anything a script can do on their client. I am not sure what happens if they send an event that doesnt exist on the server, but I would guess it would send.
Edit; It doesnt really matter, any events they send that dont exist on server will simply do nothing. They may be able to spam the event to overload data requests though.
From what I understand, @Fractality_alt is saying in certain circumstances a user can pick the quantity of what they want to buy, then of course the server multiplies the price of the item by the quantity. If the quantity is NaN, then NaN balance is removed. Of course the server finds the price of the item in question itself, it’s just that if you let the client decide quantity of what it’s buying without sanity checks it can be exploited very easily, and in some cases despite having a sanity check in place there’s a hole still.
Yea but stuff like that should already be checked for. If you assume whatever client sends is going to be what theyre supposed to send then you still havent fully understood the concept of FE. Simple checks for something like that might include num==num and num>0 and num~=1/0 and floor(num) and so on
Theres also stuff that overwatch or rocket league do but that would require a lot of physics data correction and splitting which might be difficult on roblox