www.mozilla.org/en-US/firefox/android/40.0/releasenotes/

What’s New
NEW
Support for Android Presentation API for screen casting
NEW
Added protection against unwanted software downloads
NEW
Long press on back/forward navigation buttons in app menu to bring up history list
CHANGED
JPEG images use less memory when scaled and can be painted faster
CHANGED
Sub-resources can no longer request HTTP authentication, thus protecting users from inadvertently disclosing login data
HTML5
IndexedDB transactions are now non-durable by default
HTML5
Implemented AudioBufferSourceNode.detune to modulate playback rate in cents, a logarithmic unit of measure used for musical intervals
DEVELOPER
Open links from Android applications in the same tab via EXTRA_APPLICATION_ID
FIXED
Various security fixes

This release does not have a Play Store Description, so we grabbed one from version 62.0.2:

Experience a fast, smart and personal Web. Firefox is the independent, people-first browser made by Mozilla, voted the Most Trusted Internet Company for Privacy. Upgrade today and join hundreds of millions who depend on Firefox for a more personal browsing experience.

FAST. SMART. YOURS.
Firefox is made with you in mind and gives you the power to take back control of your Web experience.
That’s why we design the product with smart features that take the guesswork out of browsing.

SEARCH INTELLIGENTLY & GET THERE FASTER
- Firefox anticipates your needs and intuitively provides multiple suggested and previously searched results across your favorite search engines. Every time.
- Easily access shortcuts to search providers including Wikipedia, Twitter and Amazon.

NEXT LEVEL PRIVACY
- Your privacy has been upgraded. Private Browsing with Tracking Protection blocks parts of Web pages that may track your browsing activity.

SYNC FIREFOX ACROSS YOUR DEVICES
- With a Firefox Account, access your history, bookmarks and open tabs from your desktop on your smartphone and tablet.
- Firefox also safely remembers your passwords across devices so you don’t have to.

INTUITIVE VISUAL TABS
- Intuitive visual and numbered tabs easily let you find content for future reference.
- Open as many tabs as you like without losing track of your open Web pages.

EASY ACCESS TO YOUR TOP SITES
- Spend your time reading your favorites sites instead of looking for them.

ADD-ONS FOR EVERYTHING
- Take control of your Web experience by personalizing Firefox with add-ons like ad blockers, password and download managers and more.

QUICK SHARE
- Firefox remembers your most recently used apps to help you easily share content to Facebook, Twitter, WhatsApp, Skype and more.

TAKE IT TO THE BIG SCREEN
- Send video and Web content from your smartphone or tablet to any TV equipped with supported streaming capabilities.

Learn more about Firefox for Android:
- Have questions or need help? Visit support.mozilla.org/mobile
- Read about Firefox permissions: mzl.la/Permissions
- Learn more about what’s up at Mozilla: blog.mozilla.org
- Like Firefox on Facebook: mzl.la/FXFacebook
- Follow Firefox on Twitter: mzl.la/FXTwitter

ABOUT MOZILLA
Mozilla exists to build the Internet as a public resource accessible to all because we believe open and free is better than closed and controlled. We build products like Firefox to promote choice and transparency and give people more control over their lives online. Learn more at www.mozilla.org

Privacy Policy: www.mozilla.org/legal/privacy/firefox.html