Nuxt is an open-source web development framework for Vue.js. From 3.1.0 until 3.21.10 and 4.5.1, an attacker can supply a top-level `as` prop to the /__nuxt_island/ endpoint and drive dynamic component resolution through <component :is>, resolveDynamicComponent, or h(). This issue is fixed in 3.21.10 and 4.5.1.

Affected: npm: nuxt

## Impact

Nuxt server islands accept props via the `/__nuxt_island/` endpoint. When an application has a server island component that forwards props directly into Vue's dynamic component resolution (`<component :is>`, `resolveDynamicComponent`, or `h()`), an attacker can pass a plain string value (rather than a component definition) to instantiate any globally-registered Vue component or any native HTML element.

For example: ```json { "as": "SomeGlobalComponent" } ```

...resolves and renders `SomeGlobalComponent` if it is globally registered, even though the attacker should only be able to drive props for the island's declared component. Similarly, `{ "as": "iframe" }` renders an `<iframe>` element.

Unlike the primary RCE vector (GHSA-9473-5f9j-94wq), this does **not** require `vue.runtimeCompiler` to be enabled. A plain string prop is sufficient to trigger component resolution. The `template`/`render` key guard that addresses the RCE vector does not block plain string values.

Some component libraries expose a polymorphic `as` / `asChild` prop that forwards its value into `<component :is>`; `@nuxt/ui` (via `reka-ui`) is a widely used example. An application is affected if such a component receives the attacker-controlled value inside a server island. Note this does not require explicit prop forwarding: island props the island component does not declare fall through as attributes onto its single root element, so an island whose root is a `reka-ui` / `@nuxt/ui` component…