Apple's new iOS 8.1.3 software incorporates a number of bug fixes while increasing the stability and performance for compatible iPhone, iPad and iPod touch models.
The update also has patches for vulnerabilities used to jailbreak iOS 8.1.2, which means with the new iOS 8.1.3 Apple kills TaiG jailbreak as well as the PP jailbreak which were recently released by an unidentified Chinese jailbreak team to jailbreak iOS 8.1.2 with support for Mac.
Users who have accidentally updated their devices to iOS 8.1.3 but wish to go back to the previous iOS version so as to retain the jailbreak, can do so via a downgrade as Apple is still signing iOS 8.1.2.
Check out the guide below if you want to downgrade to iOS 8.1.2 from iOS 8.1.3, which is compatible with the following iOS devices:
iPhone 6, iPhone 6 Plus, iPhone 5s, iPhone 5c, iPhone 5, iPhone 4S
iPad 4, iPad 3, iPad 2, iPad Air 2, iPad Air
iPad mini 3, iPad mini 2, iPad mini
iPod touch 5th generation
How to downgrade iOS 8.1.3 to iOS 8.1.2
Step-1: Head over to this page and download iOS 8.1.2 IPSW for your iOS device. Ensure that you download the correct IPSW firmware according to the model number of your device. Installing an incorrect firmware could damage the iOS device. The download size of these files ranges from 1.5GB to 2GB. Therefore, the download will take some time.
Step-2: Once you have the correct iOS firmware version downloaded, plug your iOS device into the computer using the USB cable
Step-3: Launch iTunes
Step-4: Navigate to the device's summary page and hold the Option/Alt on the keyboard. Or, Shift if you are using Windows
Step-5: While holding the key combination mentioned above, click Restore in iTunes
Step-6: Browse to the location where you have saved the IPSW file and open it. Now iTunes will begin restoring your iPhone/iPad and install iOS 8.1.2
Your device should now be running iOS 8.1.2. If you want to restore your backup, go to the device's summary page in iTunes and click on Restoring Backup. Wait for some time until the process is completed, and your device should be back on iOS 8.1.2.