A user submits https://example.invalid/report . The first DNS lookup returns a public address, so the application approves it. The server responds with a redirect to http://169.254.169.254/latest/meta-data/ . A fetch client follows automatically, and the original allow decision silently becomes authority to contact a different host. This is the SSRF boundary many URL-preview and import services miss: a URL is not one network destination . DNS answers can change, redirects introduce new des...