[TacticalCoder]

> xhost + hands that capability to every local user and, if your server listens on TCP, to the network. Even the narrower xhost +local: still trusts every UID on the box.

I'm not defending xhost or advocating to use it but... If you mention narrower version of xhost, then why stop at:

    xhost +local:

and not mention that you can do:

    xhost +si:localuser:jack

As an intriguing unrelated sidenote you can do:

    xhost +si:localuser:jack

open an app, then do:

    xhost -si:localuser:jack

and then user jack cannot, except through the app already launched, display on the X server.