---
id: CVE-2026-50146
aliases:
- GHSA-8hv8-536x-4wqp
title: 'Astro: Reflected XSS via unescaped slot name'
summary: 'Astro: Reflected XSS via unescaped slot name'
severity: high
cvss: 7.1
cwe:
- CWE-79
- CWE-80
vendor: astro
product: astro
ecosystem: npm
affected:
- astro < 6.3.3
patched:
- astro 6.3.3
published: '2026-06-16'
updated: '2026-06-16'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-8hv8-536x-4wqp'
references:
- url: 'https://github.com/withastro/astro/security/advisories/GHSA-8hv8-536x-4wqp'
- url: 'https://github.com/advisories/GHSA-8hv8-536x-4wqp'
tags:
- ghsa
- npm
epss: 0.00268
epssPercentile: 0.1924
ingestedAt: '2026-07-07T15:41:58.375Z'
---
## Overview
## Summary
When a component uses a `client:*` directive, Astro inserts named slot content into a `data-astro-template` attribute without HTML escaping the slot name allowing an attacker to break out of the attribute context and inject arbitrary HTML, resulting in reflected XSS during SSR.
This is similar to GHSA-wrwg-2hg8-v723 but exploits a different injection point.
## Vulnerable Code
`packages/astro/src/runtime/server/render/component.ts:371:376`
```ts
// component.ts:371
`${children[key]}`
```
I found that key is interpolated directly into the attribute value without proper escaping.
## Proof of Concept
For the PoC, I set up with a minimal repository with Astro 6.3.1, Node.js: v26.0.0.
**`astro.config.mjs`**
```js
import react from '@astrojs/react';
import node from '@astrojs/node';
import { defineConfig } from 'astro/config';
export default defineConfig({
output: 'server',
adapter: node({ mode: 'standalone' }),
integrations: [react()],
});
```
**`src/pages/index.astro`**
```astro
---
import Wrapper from '../components/Wrapper.jsx';
const slotName = Astro.url.searchParams.get('tab') ?? 'default';
---
content
```
**`src/components/Wrapper.jsx`**
```jsx
export default function Wrapper() { return null; }
```
**Payload:**
```
abc">