CVE-2026-72761

The webhook URL validator in `website/notifications/webhooks.py` uses
`ip.is_global` to reject non-public addresses after DNS resolution. IPv6
transition addresses (NAT64 `64:ff9b::/96`, 6to4 `2002::/16`, Teredo
`2001:0000::/32`) are classified as globally routable by IANA, so `is_global`
returns `True` even when the embedded IPv4 targets a private, loopback, or
cloud metadata destination. An attacker can register a webhook pointing at a
hostname that resolves to a transition address to bypass the SSRF guard and
exfiltrate vulnerability data to an internal endpoint.

The vulnerability was introduced on a non-release version. The fix was already done on HEAD. It only affects

organisation running the HEAD.