Debian does facilitate unattended upgrades for its operating system but it is not enabled by default due to many critical system use cases (updates must be done manually and thoroughly tested before rolling out to production system).
This section guides you on how to setup unattended upgrades in Debian.
These are the identified threats related to Debian Software.
By default, unattended-upgrades is not installed or not configured properly.
Here are the list if actions to counter the issues.
Should the requirements permit, you can enable it by following this guide: Enable Apt Unattended Upgrades with Email Notifications
That's all for hardening Debian by enabling email notification.