After upgrading check for new services as the Internet Storm Center noted after a firewall operator noted new streaming data coming to/through firewall.
Upgrading the NAS server caused a media streaming service to turn on.
And that is how it starts. After an upgrade some months ago a service is turned on, even though one does not notice.
Then some time goes by and a vulnerability opens within the system.
Now the hackers can target the system.
Check your systems with Alpha or Sigma(Σ)