It would appear that cyber criminals are not slow to catch on to the Android Master Key exploits and more examples are cropping up...
More Exploits for Android 'MasterKey' Vulnerability Turn Up in the Wild
Researchers find trojanized banking app that exploits critical Android bug
The chances are that if you have received a firmware update for your device in the last 3 or 4 months, it will have a fix for 1 of the 2 identified exploits, Bug #8219321
, but not the Bug #9695860
which Android has also issued a patch for but, as yet, has not made its way to any firmware releases yet.
You can check to see which of the Bugs you are vulnerable to by installing and running SRT AppScanner
, free from the Google Play Store.
App developers are also starting to take these exploits seriously...
Android Flaw Puts Bitcoin Wallet Apps at Risk of Theft
Some degree of protection is offered by only using the Google Play Store and ensuring that installing apps from, "Unknown sources", is deselected on your device. Antivirus software will not prevent the Master Key exploits and may, or may not, detect them after installation.
You should also ensure that you have the very latest firmware installed for your device.
In the meantime, for rooted users, there is the fix mentioned earlier.