T-Mobile has started pushing out a new update to BlackBerry Priv units on its network. Carrying the build number of AAI459 and weighing in at 126.3MB, the update brings Android security fixes fir January. Aside from the latest security patch, the update does not include any other changes - at least that's what the official release notes on the magenta carrier's website reveal. As is usually the case with OTA rollouts, it may take some time for the update to hit your device. You can manually check if it hit your device by heading to your handset's Settings menu. Source
Source: http://www.gsmarena.com/blackberry_priv_on_tmobile_starts_getting_january_security_update-news-22838.php