The obvious question is: what's the real problem with that?
A container is a container, as long as docker itself has not bug, the container can only harm the containers content.
Most problems exists in the custom created software in the container (e.g. web-services with bugs, backdoors, ....), this will be a problem for Docker, VMs, Real-Servers, whatever too.
The real problem is the interoperability of different container, if you link the whole data, without any audit, to another container, you can have a problem, but this problem is not docker specific.
A container is a container, as long as docker itself has not bug, the container can only harm the containers content.
Most problems exists in the custom created software in the container (e.g. web-services with bugs, backdoors, ....), this will be a problem for Docker, VMs, Real-Servers, whatever too.
The real problem is the interoperability of different container, if you link the whole data, without any audit, to another container, you can have a problem, but this problem is not docker specific.