Nuxt is an open-source web development framework for Vue.js. From versions 3.4.3 to before 3.21.6 and 4.0.0-alpha.1 to before 4.4.6, navigateTo() with external: true generates a server-side HTML redirect body containing a <meta http-equiv="refresh"> tag. The destination URL is only sanitized by replacing " with %22, leaving <, >, &, and ' unencoded. An attacker who can influence the URL passed to navigateTo(url, { external: true }) can break out of the content="…" attribute and inject arbitrary HTML/JavaScript that executes under the application's origin. This issue has been patched in versions 3.21.6 and 4.4.6.

Affected: npm: nuxt

### Summary `navigateTo()` with `external: true` generates a server-side HTML redirect body containing a `<meta http-equiv="refresh">` tag. The destination URL is only sanitized by replacing `"` with `%22`, leaving `<`, `>`, `&`, and `'` unencoded. An attacker who can influence the URL passed to `navigateTo(url, { external: true })` can break out of the `content="…"` attribute and inject arbitrary HTML/JavaScript that executes under the application's origin.

This is a different root cause from CVE-2024-34343 (GHSA-vf6r-87q4-2vjf), which addressed `javascript:` protocol bypass. The issue here is triggered by any valid URL containing `>`.

### Impact Applications that pass user-controlled input to `navigateTo(url, { external: true })` — typically via a `?next=` / `?redirect=` query parameter used for post-login or "return to" flows — are vulnerable to reflected cross-site scripting. The injected script runs in the context of the application's origin during the server-rendered redirect response, before the meta-refresh fires.

### Details In `packages/nuxt/src/app/composables/router.ts`, the SSR redirect path builds an HTML response body with only `"` percent-encoded in the destination URL:

```ts const encodedLoc = location.replace(/"/g, '%22') nuxtApp.ssrContext!['~renderResponse'] = { status: sanitizeStatusCode(options?.redirectCode || 302, 302), body: `<!DOCTYPE html><html><head><meta http-equiv="refresh" content="0; url=${encodedLoc}"></head></html>`, headers: { location:…