The Mozilla Developers intend to include Network Partitioning in Firefox 85 for blocking methods of tracking user movements between sites based on the storage of identifiers in areas not intended for permanent storage of information (“Supercookies”).
One type of Supercookies used by tracking systems is based a> on evaluating the presence of certain data in browser caches, for example, as a flag you can use to check for the presence of previously loaded images, fonts, certificates, stylesheets and other data caches deposited. Currently, all resources in the cache are stored in a shared namespace, regardless of the source domain, which allows one site to determine whether resources are being loaded from another site by checking if that resource is in the cache.
Protection based on network segmentation implies adding an additional attribute to the key used to fetch objects from browser caches. In addition to the URL, a binding to the primary domain from which the main page is opened is added, which will limit the cache scope for the movement tracking scripts to the current site only (the script from the iframe will not be able to check if the resource was loaded from another site).
A similar technique has been used in the Safari browser since 2013 and slated for inclusion in Chrome. The downside of this approach is decrease the efficiency of data caching, since network caches cannot be used for resources requested by different sites. Prior to the slated enablement of network sharding in Firefox 85, an experimental enablement is planned to assess the potential negative impact on performance. The privacy.partition.network_state setting is available to control the inclusion of the new security method in about: config.