Processes launched under a lightdm guest session are not confined by the /usr/lib/lightdm/lightdm-guest-session AppArmor profile in Ubuntu 16.10, Ubuntu 17.04, and Ubuntu Artful (current dev release). The processes are unconfined.
The simple test case is to log into a guest session, launch a terminal with ctrl-alt-t, and run the following command:
$ cat /proc/self/attr/current
Expected output, as seen in Ubuntu 16.04 LTS, is:
Running the command inside of an Ubuntu 16.10 and newer guest session results in: