On the Audioficionado forum, I found a post that describes the update of the firmware. I have not tried it myself, since my firmware was already at v3.0.
On the AVForum, user 3M3rson did the upgrade without the Olive website up, so the firmware is not depended on the software. Even better, John Ehringer found out how the firmware update works (or does not, in that case, he describes how to update manually…)
Note that it is entirely at your own risk!
Please verify again that your Olive is on 4.3.2 or else installing FW 3.0 will cause irreparable damage to the hardware.
• Installation of both software and Firmware updates can last up to 10 min.
• The firmware update can be installed by pressing a simple key combination.
• With the Olive turned on, press the following two buttons Top navigation button and Fast forward button, keep both buttons pressed down for 6 seconds and release. This will trigger the installation of Firmware 3.0
• Please do NOT turn off or interrupt the installation process at any time or the unit might be irreparably damaged.