Version 1.4.1 is released! Details of the changes are here.
To upgrade, follow these instructions.
On the 1.4.x branch, 2 bits of code which used to be in core were split out into separate extensions, “Contact” and “CuratedLists”. “CuratedLists” currently must be enabled and added to your config. “Contact” should be enabled and added to your config if you want to use it, but can be left if not.