As per title; if you are not OP, command issued in the fxcontrol files are not executed and the chat shows the usual message You do not have permission to use this command.
It would also be nice if no message appeared in chat every time (even though I assume this only appens to OPped players).

I second this. Same issue. This needs to be a system-executed command so this doesn't happen

Right now i have this script that makes a few particles appear around the player when they are in a certain dimension:

{
"timeout": 5,
"dimension": 10,
"command": "/execute @A ~ ~ ~ /particle townaura ~ ~ ~ 6 6 6 0.1 30 normal @A"
}

If you needed a reference to test the issue.