Tyro, We have a feature called "flying the bee" to inform you when new HiveOS versions are available and recommended for you to upgrade. A graphic of a bee will fly in and park itself near the upper right corner of your HiveManager screen when this happens.
We do not at this time have any proactive notification mechanisms for security patches. We generally will post a notice here, and if they are significant, we will also post something in the banner of the support portal. I suggest you monitor this page (http://www.aerohive.com/support/security-center/security-bulletins) if you are concerned about getting security updates.