GHSA-gj2h-2fpw-fhv9

### Summary

`UForm` and `UAuthForm` render a server-side `<form>` element with no `method` and no `action` attribute, relying on a hydrated `@submit.prevent` handler to intercept submission. If a user submits the form before Vue hydration has attached the handler (autofill plus Enter on a slow network, JS bundle blocked by CSP or CDN failure, etc.), the browser performs the native default: a `GET` to the current URL with every named field, including `<input type="password">`, serialised into the query string.

### Details

`src/runtime/components/Form.vue` (around the template's `<form>` element) emits:

```vue <component :is="parentBus ? 'div' : 'form'" :id="formId" ref="formRef" :class="ui({ class: [uiProp?.base, props.class] })" @submit.prevent="onSubmitWrapper" > ```

No `method`, no `action`. `@submit.prevent` is the only thing stopping native submission, and it only exists after hydration. `UAuthForm` composes `UForm` and inherits the same shape.

The SSR snapshot of `UAuthForm` (`test/components/__snapshots__/AuthForm.spec.ts.snap`) shows the rendered markup, with `<input type="password" name="password">` inside a `<form>` that has no `method`.

### Proof of concept

Reported by @nimonian:

1. Create a minimal Nuxt app with a `UAuthForm`. 2. Build for production and visit in a browser with network throttling at 4G or slower. 3. Enter credentials. 4. Submit (or let autofill + Enter fire before hydration).

The URL becomes `/login?email=…&password=…`. Reproducible deterministically in Playwright by triggering submit immediately on `load`.

### Impact

Any application using `UAuthForm` (or `UForm` with credential-shaped fields) as documented. The cleartext password lands in:

- the address bar, - `window.history`, - the `Referer` header of every same-origin subresource fetched from the resulting URL, - access logs of any reverse proxy, CDN, or WAF that records request URLs.

### Patch

Default the rendered `<form>` to `method="post"` so the pre-hydration fallback submits as POST rather than GET. Vue's `@submit.prevent` still intercepts the hydrated case; the attribute only matters in the race window. Applications that explicitly want native GET submission can opt back in by passing `method="get"`.

### Credit

Reported by @nimonian. Originally filed as `GHSA-92g7-2fpq-hmq8` against `nuxt/nuxt`; moved here because the affected code lives in `@nuxt/ui`.