GHSA-pfhg-q3qv-9q6r - SvelteKit: URL redirection to untrusted site via enhanced form submission

### Impact Applications using enhanced form actions (`use:enhance`) on routes that accept paths beginning with `//`, such as catch-all routes, may be vulnerable to an open redirect. ### Patches A fix has been prepared for `@sveltejs/kit` 3.0.0. Users should upgrade to 3.0.0 or later. The fix preserves leading double slashes in action paths without generating protocol-relative URLs, restricts non-redirect action navigation to the current origin, and includes the origin when comparing action locations with the current page. ### Workarounds Reject requests whose parsed URL pathname begins with `//` before route resolution, for example in a reverse proxy or a SvelteKit `handle` hook. Alternatively, disable navigation for non-redirect enhanced form results by supplying a custom submission callback: ```svelte <form method="POST" use:enhance={() => ({ update }) => update({ navigate: false })}> <!-- form fields --> </form> ``` This applies non-redirect results to the current page instead of navigating to the action location.