How android WebView can be exploited and how to secure my app from WebView vulnerability?

I heard that WebView vulnerability is active in android versions before 4.2. I read that it is fixed by google in their newer updates from 4.2. What I want to know is a brief description of the WebView vulnerability,like,how an attacker can use this vulnerability and any solution to fix this by myself in my app if it is possible to secure my android app from this vulnerabilty.