For an example lets say that a person has been selected to get an admin panel and only they and the other people can use it
In server storage, you would keep a screen gui object including the local script controlling it for your admin panel, and in the server script service, you would have a script that checks if each player that joined is an admin, and if so, it will clone the screen gui into their player so that they have access to it when they spawn in. The admin panel will have to use remote events in order to do anything to the server just like any other local script.
This will prevent any exploiters from gaining access to your admin panel because they simply will never have access to it in the first place.
local player = game.Players.LocalPlayer if player.UserId == "yourfriendsoryouruserid" then--Keep doing this until everyone you want is on there else yourgui:Destroy() end