The system can automatically install updates. If you want this, install unattended-upgrades package.vYou never miss a security update.
aptitude install unattended-upgrades
You must edit this file. Make a reconfiguration and select yes.
vi /etc/apt/apt.conf.d/50unattended-upgrades
.... Unattended-Upgrade::Allowed-Origins { "${distro_id}:${distro_codename}-security"; "${distro_id}:${distro_codename}-updates"; "${distro_id}:${distro_codename}-proposed"; "${distro_id}:${distro_codename}-backports"; }; ....
dpkg-reconfigure unattended-upgrades