Android signature verification vulnerability

I have been reading about the android signature verification vulnerability and below blog holds a solution to solve the malicious files that can be included in the apk by unzipping the apk file and including files in the META-INF folder. But I am unable to understand the solution specified here. Can anyone explain me the way by which it can be achieved.. The blog link is below..

http://blog.trustlook.com/2015/09/09/android-signature-verification-vulnerability-and-exploitation/