Echo Static File Middleware Route Protection Bypass Via Encoded Dot-dot Traversal

Summary Echo v5.2.0 contains a bypass of the fix for GHSA-vfp3-v2gw-7wfq. The fix rejects encoded path separators such as "%2F" and "%5C" before static file path unescaping, but two traversal forms still bypass route-level middleware protections for static files. The primary bypass uses encoded...