This release fixes some issues in the 4.0.2 release that have been reported.
Ubuntu: https://launchpad.net/~pulse-eight/+archive/ubuntu/libcec
Windows: https://github.com/Pulse-Eight/libcec/releases/download/libcec-4.0.3/libCEC-4.0.3.exe
It also includes an updated firmware, which addresses a bug in Samsung 2016+ models that powers on the TV randomly. You don't have to upgrade the firmware if you have another brand or an older model.
The wake up feature is disabled as a result, when a Samsung TV is detected. You can no longer wake up the PC if it's in standby or power it on when the PC is off (with an Intel NUC adapter).