>Any process you run can already access the memory and files of everything else as the same user. *When the applications themselves aren't properly sandboxed.

>Any process you run can already access the memory and files of everything else as the same user. *When the applications themselves aren't properly sandboxed. If they are with for example firejail, flatpak or snap. Then x11 is a gaping hole like having proper doors in a house but broken windows. It's not the job of the compositor to sandbox applications.