I do not think this is possible,
but I may be pleasantly surprised.....

Is it possible to enable a VM in KVM to
automatically start on host boot from inside that VM?
Meaning you log into that VM, and find a
means to enable it to auto start when its host reboots.

Yes, I know you can use virsh like the following.
But you can only do this if you are
logged into the VM's host.

Hey Fano
I just have to say, you are a pistol, dragging all this quantum probability confusion into a nice and wholesome virtualization thread (correction, a newbie thread? What were you thinking, man?). This question reeks of that damn Schrodingers cat conundrum...

I'd have to say no, since the VM doesn't exist (except as an inode) prior to instantiation of the host (i.e until the host starts it), however I have been drinking a fine Merlot so we may both yet be surprised...

so yes, basically you cannot see anything "outside" of that VM, therefore you cannot modify that host.

I heard of hackers accessing the host
through the host's VM.
Not sure if it is KVM or something other VMs.

But I am not sure since I was not interested then.
I think it may have been an article about security
breach at ARS Techica.

oh, yes, there can be security related problems, but I'm afraid I don't know about that. And obviously it will be fixed as soon as it was published.

The VM was instantiated ( a segregated namespace on the host) and therefor if you can "break-out" of the segregation, i.e. elevate you're threads effective UID,( and really, in this day and age, who supports segregation, namespace or otherwise? ) that virtual world becomes your oyster.
Once you've crossed that rubicon, you can cause all manner of mischief, much like the ancient Goths (or was it Visigoths ???).
But you have to begin with a thread, which doesn't exist prior to the instantiation of the host, unless we're going to head down the "quantum event" wormhole (i.e. is time sequential or do we just prefer it that way for reasons having to do with convenience and scheduling of the work day aka kernel scheduling).

probably that quantum issue is already solved. Who knows?

Probability doesn't survive the monty hall test. If a game show host can thwart the powers of mathematics, I for one, have no patience for them. (...much like the electoral college and for similar reasons...)
I suddenly feel the overwhelming desire to pray, I will be in the back pew of the local church if anyone needs me...