Submodules defined with relative paths are now clickable in the web UI, making it easy to navigate to linked repositories. Previously, only submodules with absolute URLs were clickable.
Only relative paths following the format ../{repo} (a repository with the same owner) or ../{owner}/{repo} (a repository with a different owner) are supported.
To learn more about submodules, see Working with submodules on the GitHub blog.
In February, we announced a simplified listing process for apps on the marketplace.
All "verified apps" on the marketplace are now updated to the validated publisher model. The listings have moved from the 
verified badge to the marketplace badge indicating the publishers, and not apps, are scrutinized.
Existing subscriptions of the apps are not impacted.
Dependency review, in beta, helps you review dependency changes in your pull requests. But how do you find your package manifests amongst all the other files? Now you can filter the files in pull requests to see just the package manifests:
What if you don’t have a pull request at all? Now you can review dependency changes between any two commits, such as:
Learn more about reviewing dependency changes in pull requests.