I found a bug that can give gamemode 1 on a server that does not give gamemode 1 to a certain extent

This exploit can allow flight on any server and the harming of other entities in this mode. You can also break blocks (limited) while in this "gamemode 1" give yourself blocks but, you cannot ban, mute, or op yourself on the server.

Here is a video to show you:

https://www.youtube.com/watch?v=OjdiR0xyXVM