TL;DR (the crucial info is, predictably, at the very end): share a picture with someone via dropbox or whatever and embed that dropbox page on a website you con

TL;DR (the crucial info is, predictably, at the very end): share a picture with someone via dropbox or whatever and embed that dropbox page on a website you control, then "analyze accessible information about the target’s browser and the behavior of their processor as the request is happening to make an inference about whether the content request was allowed or denied." So you can confirm via unspecified vectors whether a visitor is among a specific set of persons if they are logged in with the right user account. (Not exactly a way to unmask any anonymous user on any major platform, the way the headline sounds.) Edit: oh, it's not at the very end. Beyond the horizontal line and newsletter begging there's a few more paragraphs I didn't see before. Credit where it's due, they didn't bury it at the end but, instead, only 988 words stand between you and the above information!