Redirect bypass to instance metadata

Your 'import from URL' feature (a server-side PDF/HTML renderer that fetches a user-supplied link) has an allowlist blocking 169.254.169.254 and RFC1918 ranges. A bug-bounty report shows it was bypassed: the attacker supplied a URL on their own domain that returns an HTTP 302 redirect to http://169.254.169.254/latest/meta-data/iam/security-credentials/, and the renderer followed the redirect (the allowlist only checked the original URL, not the redirect target). CloudTrail now shows the renderer host's instance role used from an external IP. How do you triage the blast radius, contain it, and fix the SSRF properly?