Allwinner, a Chinese semiconductor maker, has been caught shipping a version of Linux Kernel with an easy-to-use built-in backdoor. The backdoor code is believed to have been left by mistake by the authors after completing the debugging process. Allwinner is a leading supplier of application processors that are used in many low-cost Android tablets, ARM-based PCs, set-top boxes, and other electronic devices worldwide. Backdoor code for debugging ARM-powered Android devices managed to make its way in shipped firmware after firmware makers wrote their own kernel code.
Source: https://thehackernews.com/2016/05/android-kernal-exploit.html