BonkTheAnnoyedHow are people discovering random subdomains on my server?
At the end of the day this is obscurity, not security; however obscurity is a good secondary defense because it buys time.
I too would be interested to learn how this leaked
it’s not even obscurity; it’s logged publicly.
How is it being logged publicly? Like OP said there is no specific subdomain registered in the DNS records (instead using a wildcard). Same for the SSL cert. Only things I can think of is the browser leaking the subdomains (through google or Microsoft) or the DNS queries themselves being logged and leaked. (Possibly by the ISP inspecting the traffic or logging and leaking on their own DNS servers?). I would hardly call either of those public.