Now that polished versions of Firefox 24 are out the door, Mozilla has released the beta version of Firefox 25 -- and it's quite a hefty upgrade for Android users. The new mobile build adds guest browsing, which lets friends borrow your device without seeing your bookmarks and history. As soon as a guest signs out, your data comes back. Beta testers also get a mixed content blocker, support for add-ons with page actions and an option to set pictures as contact photos or wallpapers. If you like the idea of sharing Android gadgets with others, you can grab Firefox 25 through Google Play.