@argonaut how would that be? Why would a tunnel to a docker running behind pfsense access pfsense gui?
When you resolve say something.domain.tld that is hosted on clouldflare, and then pushed down the tunnel when you access it, that would not access your pfsense wan IP and then gui port.
Now sure if something.domain.tld resolved to your pfsense wan IP, and you were running the gui on pfsense wan port, and you had that open sure they would hit your gui. But why would the gui port (443? or 80?) be open on your wan in the first place?
But none of that would have anything to do with a tunnel between a docker and clouldflare.
If your gui is exposed on your wan, they don't have to "guess" any domain, they could just hit your IP with random scan.. You understand there is going to be countless things scanning the internet, and sure on 443 and 80.. And lots of other ports - you shouldn't really ever expose pfsense gui to the public internet. If you want to access your pfsense gui while remote, it would be best to vpn to pfsense, and access the gui over the vpn.