In the nightly assemblies of Firefox, from which Firefox 127 is based, a new mechanism called “Bounce Tracking Protection” has been added in order to protect against tracking user movements. This mechanism expands the capabilities of Tracking Protection by targeting visitors who use redirects to other pages. The essence of this method lies in tracking codes redirecting users to their own websites, allowing them to store cookies and data in local storage tied to their own site rather than the site being tracked.
This preservation of data after the user has been redirected to another site enables a way to bypass Enhanced Tracking Protection (ETP) methods for blocking cross-sites. This is because the intermediate page opens outside the context of the site being tracked, giving the opportunity to freely install tracking cookies on such pages.
The Bounce Tracking Protection mechanism is designed to capture tracking activities specific to redirects, and it periodically clears cookies and locally stored data for websites utilized by well-known tracking systems. Unlike the previously available “Cookie Purging” mode, this new mechanism does not rely on a list of well-known trackers but instead utilizes heuristics to identify new tracking sites by analyzing behavior following redirects.