Do you like DNS-over-HTTPS? Well, I'm proxying https://dns.google/! Would be cool if you can find an XSS!

Report to admin locally:

curl http://localhost:8008/report -H "Content-Type: application/json" -d '{"url":"http://proxy/"}'

Report to admin for the real flag:

curl https://dnxss.chal-kalmarc.tf/report -H "Content-Type: application/json" -d '{"url":"http://proxy/"}'