[Google] now only fixing bugs found in the two most recent versions of Android known as Kitkat (4.4) and Lollipop (5.0).
[…]
“It would appear that over 930 million Android phones are now out of official Google security patch support”

via http://www.bbc.com/news/technology-30795253

Android’s take on security

Android

a central crowdsourced resource for complete and up-to-date Android content and tutorials

Android

CodePath Android Cliffnotes

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