Android has a lot (really, A LOT) of severe security issues that could compromise your phone and data. The Android VTS tool has been out for some time, and the latest version will help you in detecting all system vulnerabilities (known as CVEs). That's the good news.
The bad news is it won't patch nor fix them since that's the work of your phone's vendor, meaning there are little chances you'll get them solved unless you a have recent flagship device.
The app was pulled from the PlayStore some weeks ago (maybe because it was a direct hit at Google), but can still be downloaded from the official GitHub page:
https://github.com/nowsecure/android-vts/releases
Even though my phone is running Lollipop 5.1.1, the app detected 5 vulnerabilities, which confirms that having the "latest" android version doesn't mean your phone is protected.