I'm having the same issue.
https://securitytrails.com/ also had my "secret" staging subdomain.
I made a catch-all certificate, so the subdomain didn't show up in CT logs.
It's still a secret to me how my subdomain ended up in their database.
https://securitytrails.com/ also had my "secret" staging subdomain.
I made a catch-all certificate, so the subdomain didn't show up in CT logs.
It's still a secret to me how my subdomain ended up in their database.
If you delegate a subdomain through Cloudflare to your own DNS servers, from what I remember from the animal book, the recursive server should ask Cloudflare for the address of the machine to which the delegation has been made (yours), and while any further resolutions would be answered by your machine, Cloudflare would at very least know of every query to that subdomain.
If you delegate a subdomain and have subdomains under that subdomain, then Cloudflare would only see resolutions to that subdomain and not to the sub-subdomains.
In other words, for most things, they'd have full insight.