However, some users may have concerns about the security issues of this feature but there is no need to worry as this session runs in a restricted environment with a high level of security so the Guest Session user cannot access your files or informations.
Still not convinced ?
OK, then i will show you how to disable it:
gksudo gedit /etc/lightdm/lightdm.conf
allow-guest=falseto the end of the file. After this modification, your lightdm.conf file should look something like this: