According to the Microsoft Lumia support page, the update is described as 01078.00027.15506.02005 – where the last two digits determine the specific device. Below is the breakdown of what’s new with the December firmware update for Lumia 950 and Lumia 950 XL:

Stability and performance improvements. Improvements for SD memory card support. Improvements for automatic display brightness settings. Fix for a camera problem that was causing noisy images in low-light conditions for some users. Fix for a 4K video problem that was causing stripes to show up while playing back recorded videos for some users.

It’s worth pointing out that the new firmware update (01078.00027.15506.02005) isn’t available for Lumia 550. As always the firmware will download and install automatically, but you can always check for new update manually by going to Settings > Update & security > Phone update and tapping the Check for updates button. If you don’t see the firmware update, give it sometime and check back. Source Microsoft Lumia Via  Microsoft Answers All content on this site is provided with no warranties, express or implied. Use any information at your own risk. Always backup of your device and files before making any changes. Privacy policy info.