An update is now available for those with the BlackBerry Priv, and this update also focuses on security. We've seen monthly security patches since the phone's release, but this is a bit different. A recent discovery showed that the Android / Linux kernel was vulnerable to a specific attack, and this update fixes that to prevent issues. It's likely that these are the same patches to the Android base that Google says they are rolling out to Nexus devices this week, though it's possible that BlackBerry has added some of their own additional enhancements. For everyone who was hoping, no, it's not Marshmallow.
BlackBerry has posted additional details on the update:
This advisory addresses an industry-wide elevation of privilege vulnerability that is not currently being exploited against, but affects, BlackBerry® PRIV smartphones. BlackBerry customer risk is limited by the inability of a potential attacker to force exploitation of the vulnerability without customer interaction. Successful exploitation requires an attacker craft a malicious application (app) and that a user install the malicious app. If the requirements are met for exploitation, an attacker could potentially gain locally elevated privileges. After installing the recommended software update, affected customers will be fully protected from this vulnerability.
If you purchased your Priv from ShopBlackBerry, you should see an update available on your phone. If you aren't yet noticing the update, you can head into Settings, About phone and check manually for the update.