Ah, more than a decade ago I found a similar issue on Friendster (anyone remember them?), I could embed an HTML image tag in my profile which loaded a PHP scrip

Ah, more than a decade ago I found a similar issue on Friendster (anyone remember them?), I could embed an HTML image tag in my profile which loaded a PHP script (under my control) that would redirect the user to something like friendster.com/poke?id=[my user id], so if anyone visited my profile, their browser would GET that URL and I'd get a "poke" (I don't remember the Friendster term for it), notifying me who visited my profile. I didn't get many pokes, and I can't tell what part of this story is the saddest. Maybe the part that there probably weren't bounties back then (that I was aware of) and I didn't get any money for this discovery.