CVE-2026-46431: Permissive Cross-domain Policy with Untrusted Domains

Algernon is a small self-contained pure-Go web server. Prior to 1.17.7, the SSE event server's Access-Control-Allow-Origin response header was hardcoded to the wildcard regardless of the caller's Origin. Because EventSource does not preflight and does not send cookies, the wildcard is sufficient ...