As Nokia has started rolling out Windows Phone Tango/Mango refresh updates(7.10.8773.98) to Nokia Lumia 800 and Lumia 710 devices, some early adopters have found the way to download Windows Phone updates as cab files. If you are in the urge to try these updates, you can download the cab files and update your Windows Phone device manually. For your information, this is not an official method to update your phone. Please wait for official update to make sure of your device warranties and get proper firmware update from your device OEM.
Check out the XDA-Developers thread here to update to Windows Phone Tango.
Thanks Bobzero for the heads up.