Is this a sign I got hacked?

I was doing some important stuff on VirtualBox. I reinstalled my Mac brand new, installed VirtualBox from VirtualBox.org, and installed Ubuntu Server 20.04.

After finishing my work I typed poweroff (I only have one administrator account). Now I haven’t even installed openssh upon installing Ubuntu, no connection whatsoever to the outside world of this VirtualBox except some very trustworthy installations.

And I get this message:

Failed to set wall message, ignoring: Interactive authentication required
Failed to power off system via login:d: Interactive authentication required.
Failed to open initctl fifo: Permission denied
Failed to talk to init daemon

Does that mean somebody else was also using or sneaking into my VirtualBox guest OS?

And by the way, I verified the checksum of the download of my VirtualBox AND of my ubuntu installation!