SilverStripe 3.3.1-rc1, 3.2.3-rc1 and 3.1.18-rc1 have been released to resolve a breaking issue with gridfield buttons in the most recent release for each version.
Changelogs for each of these releases can be found at the below locations:
To get setup, you can install this using composer (as below):
composer create-project silverstripe/installer ./ss33 3.3.1-rc1
You can also download pre-built zip / tar from http://www.silverstripe.org/download.
Damian Mooyman | Senior Platform Developer