Online

In the webinterface of the Maxwell 10 go to: 

Settings - System - Firmware update

Data server URL = http://profile.gigaset.net/device/ift/

Click on Update firmware and the latest Firmware that is online will be downloaded.

Manual

First download the Firmware on your PC and unpack the zip file. You will get a .txt file with the Open Source License text and an encrypted zip file which is your firmware image.

In the webinterface of the Maxwell 10 go to:

Settings - System - Firmware update

Click on "Choose File" and select the Firmware file.

Click on "Load" to start the upgrade.