It happened in the early morning, at 5 AM, while I'm sleeping. Unattended-upgrades checks for updates. It ran and downloaded the patch along with the regular updates. It sent a mail to root which is sent to me, or my regular email.
So I know that the update manager ran and downloaded the packages. Installed it. But see the warning below the header! A reboot is required because the kernel is involved. To finish the kernel install I have to reboot the system.