In February, Mozilla announced to start blocking cookies from third-party advertisers in release 22 by default. But, it has back tracked from turning on default Firefox cookie blocking from third-parties in version 22 to fine tune the feature.
Mozilla’s Brendan Eich revealed in his personal blog that a patch from Jonathan Mayer is being tested currently. The patch mimics how Safari’s cooki blocking works – allowing cookies from sites already visited, and blocking cookies from sites not visited yet.
However, this approach has two issues. One is being called false positives. That is, sites which use multiple domains to serve content and cookies to a single domain would be blocked unnecessarily from being storing cookies. The other issue is of false negatives. That is, sites which you visited once, but don’t want to be tracked by will be able to store cookies.
These two shortcomings compelled Mozilla to delay default Firefox cookie blocking from third-parties in version 22. But, we won’t have to wait much longer. Eich wrote, “We will update all of you within six weeks so you can understand our thinking and how we will proceed.”