La historia resumida seria hay bug grave de seguridad en los Exynos-kernel de la serie 4...
Segun Samsung:
Samsung is aware of the potential security issue related to the Exynos processor and plans to provide a software update to address it as quickly as possible.

The issue may arise only when a malicious application is operated on the affected devices; however, this does not affect most devices operating credible and authenticated applications.

[ROOT][SECURITY] Root exploit on Exynos - xda-developers

Como dice hay, facil root... demasiado facil q es un peligro, osea, ojo con bajar apk por google.
Los afectados
Galaxy S2, S3, Note, Note2 etc
Para saber, bajas por play store "exynos mem bug checker"
y si tenes el bug, podes rootearlo limpiamente y/o patchearlo

[ROOT EXPLOIT+PATCH][2012.12.19] ExynosAbuse APK v1.40 - xda-developers

Tengo la note2 con el bug, termine rooteandolo y patcheando..... aunque no tenga idea de pq lo rootee xD