Vite XSS vulnerability in `server.transformIndexHtml` via URL payload
Date: 2023-12
Affected: npm/vite, npm/vite, npm/vite
Attack vector: xss
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2023-49293
CWE: CWE-79
CVSS: 6.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N)

### Summary When Vite's HTML transformation is invoked manually via `server.transformIndexHtml`, the original request URL is passed in unmodified, and the `html` being transformed contains inline module scripts (`<script type="module">...</script>`), it is possible to inject arbitrary HTML into the transformed output by supplying a malicious URL query string to `server.transformIndexHtml`. ### Impact Only apps using `appType: 'custom'` and using the default Vite HTML middleware are affected. The HTML entry must also contain an inline script. The attack requires a user to click on a malicious URL while running the dev server. Restricted files aren't exposed to the attacker. ### Patches Fixed in vite@5.0.5, vite@4.5.1, vite@4.4.12 ### Details Suppose `index.html` contains an inline module script: ```html <script type="module"> // Inline script </script> ``` This script is transformed into a proxy script like ```html <script type="module" src="/index.html?html-proxy&index=0.js"></script> ``` due to Vite's HTML plugin: https://github.com/vitejs/vite/blob/7fd7c6cebfcad34ae7021ebee28f97b1f28ef3f3/packages/vite/src/node/plugins/html.ts#L429-L465 When `appType: 'spa' | 'mpa'`, Vite serves HTML itself, and `htmlFallbackMiddleware` rewrites `req.url` to the canonical path of `index.html`, https://github.com/vitejs/vite/blob/73ef074b80fa7252e0c46a37a2c94ba8cba46504/packages/vite/src/node/server/middlewares/htmlFallback.ts#L44-L47 so the `url` passed to `server.transformInde


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