Hmm this is a bit of an interesting question. The original study (2012) exploited a security bug, which let anyone see which sites you had visited. (Basically,

Hmm this is a bit of an interesting question. The original study (2012) exploited a security bug, which let anyone see which sites you had visited. (Basically, by checking the color of links with JS to see if :visited styling had been applied.) That bug doesn't exist anymore, and the new survey just uses opt-in data to "confirm" it. So, I don't actually think this research is particularly relevant anymore? It can't really be exploited (and when it can, there's much better ways to track the person).