Requires the Xposed Framework. Grab it at http://forum.xda-developers.com/showthread.php?t=1574401 and make sure it runs properly on your device.
ROOT only required for installing the Xposed Framework it can be dropped afterwards.

This app patches several vulnerability issues found on Android collectively known as 'Master Key' exploits:
- bug 8219321
- bug 9695860
- bug 9950697

In general terms these allow exploiting signed APKs by replacing the code they contain while maintaining the existing signature valid (hence the term 'Master Key') leading you to think the original author is someone you trust.
The original Android sources have been corrected to fix these problems but it might take a while
till stock ROMs include the fixes if ever.

To check if you're vulnerable you can use other apps available on the store such as SRT AppScanner (https://play.google.com/store/apps/details?id=de.backessrt.appintegrity) or Bluebox Security Scanner (https://play.google.com/store/apps/details?id=com.bluebox.labs.onerootscanner).
Note: If using Bluebox Security Scanner make sure to force a refresh on the app once the fix is applied otherwise you might get a cached and incorrect result.

For any questions or to support my work please visit http://forum.xda-developers.com/showthread.php?t=2365294