Google recently made a promise to deliver monthly updates to Android smartphones and tablets with one goal, improve security. Rather than patch potential problems or vulnerabilities a few times a year, or worse, wait for manufacturers to do it, we get security updates once a month. The company has done an excellent job with it, and released them within the first week each and every month since.
Lately we've seen big potential Android malware issues like Hummingbad or Stagefright, but they've both been shut down because Google patched the exploits in monthly security updates.
Android 7.1.1 Nougat is rolling out right now. It runs the latest and most secure software, including the December security patches. If you're concerned about security, install Android 7.1.1 Nougat right away. Then of course, always use a lockscreen secure method.