> it was exposed to the internet, with open ports in the router firewall
Upvoted because you're right that the comments in this thread have nothing to do with what happened here.
The story would have been no different if OP had created an Alpine Linux container and exposed SSH to the internet with SSH password authentication enabled and a weak password.
It's nothing to do with Docker's firewalling.
What? The story would have been VERY different, obviously that's asking for trouble. Opening a port to your database running in a docker container is not a remote execution vulnerability, or if it is, the article is failing to explain how.