Traefik: BasicAuth singleflight coalescing reintroduces an unauthenticated username-enumeration timing oracle

Summary Traefik's BasicAuth middleware coalesces concurrent credential checks through a singleflight.Group to avoid hashing the same password many times at once. Since v3.6.11 the deduplication key was built from the submitted password plus the stored secret, so it depended on server state: a...