On myxc2xa0Samsung Galaxy Note phone I started receiving strange notifications in Mandarin (the language of the people of China). Once I click on the notification it opens my browser with a blank page and then exits just after few seconds.
A few minutes later I get this app install prompt:
It says in French
blocked install of apps not coming from Android market.
This has been repeating several times since ~2 weeks now.
My phone has the latest updates offered by Samsung and is not rooted. I also did not install any app in Mandarin.
I would say the app is Baidu Browser or any other app from Baidu.
Despite not being able to see an app in the laucher, you could have some sort of malware app installed that will only display notify items but stood hidden in background. On your phone go to Settings > Application Manager and check for all the apps you have installed. If you find an app that you haven't installed, uninstalling it might end the notification issues.
If you only install apps from Google's Play Store I would suggest you disable the Unknown source option to enable/disable the installation of third party app (if you have this option enabled). You can find the option in either Settings > Security, Settings > Developement or Settings > Application Manager (depending on your Android version)
As for the ROM and updates, they can't do anything about malware apps.