[alexlarsson]

You didn't give the root command. But the app can easily send keyboard input events to your terminal window injecting that command.

[koffiezet]

That's not a Docker issue, that's an X11 issue. Unless you're using Wayland, you don't have much choice here.

[heavenlyhash]

You have lots of choices. Try making another X server with Xephyr and connecting to that, for example.