One piece of information a lot of places are clamoring to get their hands on is what other websites their visitors are viewing. By having access to this information they would be able to determine what social networks you use, what search engine you prefer, and more. As it turns out any site can grab this information from your browser, but there’s one little catch.
This is making use of a standard web browser feature that makes it possible for the user to distinguish which links/sites they’ve visited, and so it really isn’t a vulnerability. Luckily this doesn’t spit out information like how many times a user has visited a particular site, but I’m sure that won’t provide too much comfort to you.
The catch? As you might have realized by now this will only work using a pre-defined list of sites, and it can’t actually crawl through your browser’s history. That’s not stopping people from implementing it though. Using SocialHistory this site has already put together a system that will guess whether you’re male or female based upon the sites you visit. It says that they’re not storing any of the data, but I’m sure other sites who are trying to sneakily gather the stats won’t be so forthcoming about their intentions.