Mozilla released Firefox v27 this week, the latest version of their Firefox browser.
The major new feature added is the ability to run more than one social service at once. New services were added too, which you can read about here.
Also, as usual, a number of issues were corrected from v26. You can see the complete list Firefox's v27.0 Bug Fixes page.
You can download Firefox v27 here, or just watch for the update notification next time you're using the browser. Check out the Firefox v27.0 Release Notes for an overview of what you're getting in this new version.