Thomas Fox-Brewster who is from a website called Forbes states that Google has stopped pushing security updates to the WebView tool if you are using Android 4.3 Jelly Bean (or any earlier flavour of Android).

This all happened without warning.  There are 949 devices that are running these versions of the Android os that can be affected at anytime.

Over 60% of Android devices which connected to Google Play between Dec 30 2014 and Jan 5 2015 (via Google’s Android dashboard) ran the older version of Android. All of these devices will no longer receive the security updates.

Google when asked refused to answer this question.

Reference: Appalled security researchers and Forbes