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Install Rooted Android 4.2.1 Jelly Bean XXUFMB3 leaked firmware for the Samsung Galaxy S3 I9300

The Android 4.2.1 Jelly Bean has been leaked for the Samsung Galaxy S3 model number I9300. We’ve already posted a guide on how to flash the Stock version of the firmware and now you can install the rooted variant of the leaked Android 4.2.1 XXUFMB3 leaked firmware, use this tutorial to install it.

After only a day, XDA members and developers started to work on releasing a rooted variant of the JOP40D JB 4.2.1 ROM. Now this variant is ready for installation and you can learn how to successfully apply it by reading the instructions posted in this article. You should make sure to read the entire post first and only when you’re sure that you can complete it without problems, you should proceed to the ‘how-to’ post. Remember that, usually, these guides are destined to be used by advanced Android users.

Also, you should take a look at the preparation guide below, too. It will teach you what steps should be taken before installing a new ROM on an Android device. Also, you’ll learn how to backup apps and other data that you don’t want to lose while installing a new OS.

The Android 4.2.1 JB JOP40D.XXUMFB3 firmware that you’ll find in this post has been rooted, fully zipaligned, deodexed, busyboxed, init.d support added, insecure kernel, updated Adfree Hosts and all the carrier bloatware has been fully removed. In order to successfully install this firmware on your I9300 device you will first need to read the preparation guide below:

  • Use this tutorial only for the Samsung Galaxy S3 model number I9300. Do not attempt to flash this rooted ROM on any other Android device, as you will end up bricking it.
  • It would be better if your Galaxy S3 is running the Android 4.1.2 firmware, but this update should work on any other device.
  • Also, your phone should already be rooted and running the ClockworkMod (CWM) Recovery image. Without these you won’t be able to flash the new firmware update.
  • Use the CWM Recovery to create a full NANDROID backup of the current ROM. This will serve as a backup in case your Galaxy S3 is unable to boot after installation is complete.
  • Wipe data/ factory reset is recommended but not mandatory. However, it would be better for you to backup SMS, Call Logs and other data that is usually stored on the /system partition. The data on the internal SDcard is safe and you shouldn’t lose any of those files. Use the following tools to backup SMS and other similar data: SMS backup & restore | Call Logs backup & restore | APN Settings Backup & Restore | AppBack for Android application. Root access will be asked by these apps.
  • Also, sync your Contacts / People with the Gmail account that’s assigned to your device.
  • Make sure that your device’s battery has enough power left so that it won’t switch off while you’re updating its firmware.
  • Read the entire tutorial and make sure that you don’t skip any steps that I’ve listed below.
  • Note that we cannot be blamed in case you brick your device or you lose any data in the process.
  • In case you have problems completing the installation, then you should ask for more help in comments.

Now that you know all of the above you can get to the tutorial below.

How to update Samsung Galaxy S3 with rooted Android 4.2.1 Jelly Bean leaked stock ROM:

  1. Download the rooted I9300XXUFMB3 Android 4.2.2 ROM from HERE. Save it on your PC or directly to your device’s internal SDcard. Don’t extract its contents.
  2. Connect the phone to your PC via USB cable. Move the file on your device’s internal SDcard if you downloaded the file on to your PC. Disconnect the SGS3 from computer when the file is copied.
  3. Power off your smartphone.
  4. Boot it into CWM Recovery by pressing and holding simultaneously Volume Up, Home and Power. Release the buttons when the ClockworkMod Recovery mode appears.
  5. RECOMMENDED: Select ‘wipe data/ factory reset’ option and confirm this process. This will delete all contents that are stored on your device’s /system partition. If you don’t apply this step and the device refuses to boot after installation is complete, then you will be forced to repeat the entire tutorial guide and ‘factory reset’ the smartphone. Get to the next step when done.
  6. Select ‘install zip from sdcard’ and then ‘choose zip from sdcard’. Find the I9300XXUFMB3-Deodexed zip and confirm that you want to install it.
  7. After the ROM is installed you should return to the main menu.
  8. Select ‘reboot system now’.
  9. Wait for the first boot process to complete and then you can take control over your device once again.
  10. Test the new ROM and then tell us in comments which are its best new features.

These were all the steps that you had to take in order to flash the Rooted Jelly Bean 4.2.1 ROM on your Galaxy S3.

In case the installation cannot be complete at your first attempt, then you should repeat the entire tutorial until you manage to install it. Make sure that you apply step 5.

Test the new ROM and then you should leave a comment at the end of this post telling us if you like the new ROM and what are its best new functions. Also, you can use the comments field to ask for any other help and we will try to help you.

NOTE: if you want the Samsung-themed Android 4.2.1 JB ROM then you can use the guide HERE. It features all the Samsung bloatware such as Touchwiz and all the other functions.

I hope that you found this guide helpful and that you managed to update your device. Remember to return here as you will find numerous other ‘how-to’ guides that will allow you to keep up with the latest Android trends.

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