This is a major release for the project that provides new functionality (eg. WFS data indexing, a new REST API), helping all those that need to publish their data, services and maps with standardized metadata.
If you have any improvements you want to contribute back, the best is to use git to get a local copy of the source code, apply the fix and put out a Pull request so your improvements can be integrated quickly. Otherwise you can also create new Tickets in the issue tracker: https://github.com/geonetwork/core-geonetwork/issues
Thanks and congratulations to the all community members and developers that have been putting a huge amount of effort and energy in this release!