It is possible to be in creative mode with out cheats enabled

steps to reproduce

• Create world
• backup world ( copy the folder elsewhere )
• Launch world
• Enable cheats
• Set personal mode to 'creative'
• save & quit
• restore the backup of the world

The world will once again be in survival mode, cheats will never have been enabled ( it will warn that enabling it will disable achievements ) and you will be in creative mode while the world is in survival.

Now I've not tested this with XBOX Live, because I do not use it but given that you still get the warning I think it's safe to assume that it will work thus making this an exploit.

If it's not feel free to change the security level.

It should still be fixed tho as you expect your inventory and game mode to return to what it was in the save game.