This Meta-owned subdomain was taken over via a dangling Route53 NS delegation.
This page is served by an unauthorized third party (bug bounty researcher @debsec) over a valid Let's Encrypt TLS certificate issued for this exact hostname.
Benign proof-of-concept. No Meta data accessed. Canary: debsec-bugbounty-poc-dangling-ns-takeover-20261005T184845Z