Is cheating possible in Unity WebGL game with Photon Pun 2 Network?

I have some questions about Unity and Photon Pun 2.

1. Is WebGL game secure from hacking or cheating?
2. Is cheating a problem if the game only has private rooms?
3. If cheating is possible (as I think), then how can I protect my game from it?

I looked for an answer on the internet, but didn't find it