"People tend to believe that an OS upgrade makes their mobile devices much securer [sic] and more reliable, because the new OS version presumably fixes security loopholes and enhances the system’s security protection," the researchers point out.
But these newly discovered vulnerabilities - dubbed Pileup (privilege escalation through updating) by the researchers - exist in almost all Android versions, and allow "unprivileged" apps to automatically acquire potentially malicious capabilities - including all new permissions added by the newer version of the OS - without the users’ consent.
"The consequences of the attacks are dire, depending on the exploit opportunities on different Android devices, that is, the nature of the new resources on the target version of an update," they note.
"As an example, on various versions of Android, an upgrade allows the unprivileged malware to get the permissions for accessing voicemails, user credentials, call logs, notifications of other apps, sending SMS, starting any activity regardless of permission protection or export state, etc," they explained.
They proved their point by creating apps that exploit the aforementioned flaws and successfully submitted them to a variety of Android app markets, including Google Play.
But they have also created a security app that checks whether the apps already installed on the device will acquire malicious capabilities once the user upgrades his or her Android installation. The app is named Secure Update Scanner, and is available for download on Google Play, Amazon AppStore for Android, GetJar, SlideMe, and 360 Mobile Assistant.
The researchers have also notified Google of the flaws, and one has already been patched. But even if all get patched immediately, the Android ecosystem is painfully slow when it comes to pushing out and adopting new updates, so the app is still your best bet.