Presumably a container has network access of some sort? Malicious code could start probing and attacking anything exposed that way.
>> this will be a problem for Docker, VMs, Real-Servers, whatever too.
The implication is that you wouldn't get into this situation with a 'Real-Server' so easily, because you wouldn't just download an image and run it, without having an update/patch strategy or having much more idea of what's going on inside it.