Data exfiltration from internal networks in github.com/docker/docker

dockerd forwards DNS requests to the host loopback device, bypassing the container network namespace’s normal routing semantics, networks marked as ‘internal’ can unexpectedly forward DNS requests to an external nameserver. By registering a domain for which they control the authoritative nameservers, an attacker could arrange for a compromised container to exfiltrate data by encoding it in DNS queries that will eventually be answered by their nameservers.