Hummm probably, with your username, loads an iframe from HN (thus giving access to your logged in cookie)... and GETs or POSTs to some page, something like: GE

Hummm probably, with your username, loads an iframe from HN (thus giving access to your logged in cookie)... and GETs or POSTs to some page, something like: GET /vote?story_id=12345&username=inerte