Let me list some of the ways that precious subdomain could have been leaked 1) CZDS/DNS record sharing program 2) CT Logs 3) Browser SCT audit 4) Browser te

Let me list some of the ways that precious subdomain could have been leaked 1) CZDS/DNS record sharing program 2) CT Logs 3) Browser SCT audit 4) Browser telemetry 5) DNS logs 6) DPI 7) Antivirus/OS telemetry 8) Virus/Malware/Tracker 9) Brute forcing DNS records 10) DNSSEC 11) Server softwares with AutoTLS 12) Servers screaming their hostnames over any protocol/banner thing 13) Typing anything on the browser search bar 14) Posting it anywhere And many other novel ways I can't think of right now. I have successfully hidden some of my subdomains in the past but it definitely requires dedication. Simple silly mistakes can make all your efforts go waste. Ask any red/blue teamer. Want to hide something? Roll everything on your own.