CVE-2026-30242 Plane: SSRF via Incomplete IP Validation in Webhook URL Serializer

Plane is an an open-source project management tool. Prior to version 1.2.3, the webhook URL validation in plane/app/serializers/webhook.py only checks ip.isloopback, allowing attackers with workspace ADMIN role to create webhooks pointing to private/internal network addresses 10.x.x.x, 172.16.x.x...