@voxpelli ha, I wonder if you can CSP ban a non-existent url (https://nope.nope or something) with Content-Security-Policy-Report-Only and then in CSS do *:hover { background-image: url(https://nope.nope); } to get a URL ping any time anybody mouses over anything :)
@sil Would that report actual user-agent and not just the frozen user-agent string? 😅