5.3.3 is now available. This update includes more SEO improvements, new design controls, improved user search, bulk user editing, update support for marketplace addons, improved mail and user profile support, a host of bug fixes, and a completely overhauled attributes framework for add-on developers.
A complete list of changes is available here
You can download concrete5 5.3.3 from here:
Important note: If you are upgrading to 5.3.3. from a previous version of concrete5, please read these important instructions.