Roblox implemented FilteringEnabled to ensure that the server, not the client, has authority over game mechanics. Now, actions taken on a player's client must be sent to the server, which then decides whether to allow that action. If a player tries to create an item that doesn't exist, the server will block it.
The use of scripts must comply with the game's terms of service and end-user license agreements. Some games prohibit modding or scripting entirely, while others may encourage it. FE Ak-47 Script
Exploiters look for "Remote Exploitation." If a developer trusts the client blindly, an exploit script can abuse the system: not the client