The "unstable_redirect()" helper exported from "waku/router/server" ("packages/waku/src/router/define-router.tsx:156–161") accepts an arbitrary string and reflects it unchanged into the HTTP "Location" response header with no URL validation, scheme restriction, or path-only enforcement. Any application that passes user-controlled input to this helper — the natural pattern documented in the JSDoc and official fixtures — is vulnerable to open redirect attacks. An attacker who convinces a victim to click a crafted link can silently redirect the browser to an arbitrary external domain, enabling phishing, credential harvesting, and OAuth token theft. Additionally, scheme-relative URLs ("//evil.example/") bypass naive "https?://"-only allow-list filters that developers might add as ad-hoc mitigations. Dynamic PoC confirmed against waku 1.0.0-beta.0 (commit "8e9f542") in an isolated Docker environment. Two independent dynamic runs produced identical results. ***