I need help preventing abuse exploitng

This game uses LeftControl and Space key to go up the stairs. (userinputservice)

All scripts, except for loading maps, work on clients and are vulnerable to hackers.
Could you tell me any ideas to prevent exploiting?

It might help to understand what this comment means:

I press LeftControl and Space keys to go up the stairs.

I’m sorry for my poor english
This game uses LeftControl and Space to go up the stairs.