SilverStripe 3.3.0, 3.2.2 and 3.1.17 have been released, and include a number of security fixes of low to important severity.
The changelogs, upgrading notes, and other important information are available on the release notes pages for the appropriate releases:
To get setup, you can install this using composer (as below):
Damian Mooyman | Senior Platform Developer
SilverStripe