With the release of Android 13 for the Pixel 6 and 6a, Google posted an interesting warning on the system image website: Once you install Android 13, you can never go back to the old version. This is still the case for anyone who needs a fully featured phone, but now Google has published an Android 12 “developer support image “that will allow developers to rollback their phones even after an update. The “Developer”branding on the image means that it is not fully functional, but it will be enough to test the application.
The reason behind Google’s one-way Android 13 update is a bootloader vulnerability. The bug is on the Pixel 6, 6 Pro, and 6a, so only those pixels received the one-way update. Android 13 has a fix for the bootloader vulnerability, and to prevent attackers from rolling back the device to bypass the patch, the company has enabled rollback protection on the Pixel 6 and 6a. Rollback protection blows a physical fuse inside the phone’s SoC. There are several such fuses, and each OS version has a count of the expected number of blown fuses. If the number is too high, it means that Google has flagged this OS as insecure and obsolete and it will no longer boot.
This “developer support image”is new territory for Google. The company says that this special Android 12 image fixes the bootloader bug and increases the fuse counter so it still boots. However, it will not receive any automatic updates and is not approved by the Compatibility Test Suite (CTS). CTS is a check that promises that the OS is not modified, rooted and secure, and some banking applications and online games require this check to work. You’ll also need to perform a full device wipe if you ever want to go back to regular “public”builds and updates.
If you’re still interested, Google has Android 12 and 12L builds for the Pixel 6, 6 Pro, and 6a at developer.android.com.