If you’re on a Wayland desktop system (such as Ubuntu ≥ 17.10) and install/upgrade a VirtualBox Extension Pack, you may get a “can’t find Xauthority” popup error.
- on login screen select X11 login
- install the VirtualBox Expansion Pack
- if you desire, logout and switch back to the default login (with Wayland). VirtualBox will work in Wayland.