An anonymous reader quotes a report from Gizmodo:
Researchers at Mozilla announced this week the launch of its “Facebook Pixel Hunt” study, which seeks to track the company’s immense web-wide tracking network and investigate the intel it’s collecting on users. As the name suggests, this study is focused on a piece of tracking tech known as the “Facebook pixel.” Chances are, you’ve visited a site that uses it; these tiny pieces of tech are buried in literally millions of sites across the web, from online stores to news outlets to… well, you name it. In exchange for onboarding a free pixel on their site, these sites can then track their own visitors and microtarget ads with the same sort of precision you’d expect from a data-hungry company like Facebook.
In exchange for giving these sites the power to track every pageview, purchase, search query, and much, much more, Facebook (naturally) requires that this data be shared with it, too. In cases where the website visitor has an account on some Facebook platform, this offsite data just gets glombed onto whatever Facebook already knows about that person. If they don’t have a Facebook account, then the company collects that data anyway, and uses it to create a “shadow profile” of that particular person. These are the sorts of shadowy practices that Mozilla’s team wants to research with this study – and you can help them do it if you’re a Firefox user. Mozilla teamed up with reporters from the Markup to gather details about Facebook tracking using a free-to-download browser extension, Mozilla Rally, that will hoover up data sent out by Facebook’s pixels as you browse across the web. Aside from that data, the extension also keeps track of the time spent on different web pages, the URLs that the browser visits, and more. Mozilla was quick to note in its announcement that the only data being exported from the extension will be de-identified, and not shared with any third parties besides the Markup’s reporters.