As you already know, in the last quarter of 2016 bug/vulnerability was explored called "DirtyCow" which was in Linux Kernel for 9 years
Google fixed the vulnerability in upstream devices with latest security bulletins but the vulnerability is still affecting billions of devices (from android 2.3 to android 7.1) unfortunatly
And with "DirtyCow" new rot techniques were developed, (e.g LG V20 rooter and universal rom debloater)
*** And if you wonder "DirtyCow" vulnerability affects your device or not here it is, you can check it yourself by using this simple app "DirtyCow Checker"
Google Play Store: https://play.google.com/store/apps/d...dred.testdirty
No root is required, no ads, its free, if you like my work , you can support me by rating app in here and playstore thanx
EDIT: google strangely removed my app from playstore (i explained better in the above replies, you can look) here is the apk file of latest build: http://www.mediafire.com/file/6tjakn...ow-Checker.apk