Few hours ago Apple released iOS 4.3.4. iOS 4.3.4 doesn’t bring any new feature but it only fixes the PDF exploit in Safari that is used in JailbreakMe 3.0 to jailbreak iPad 2 and other idevices running on iOS 4.3.3.
As you know whenever you connect your device with iTunes after Apple releases a new firmware, you get a pop-up message reading that a new software is available for your device provided your device is still on older iOS version. But when you update your device to this latest firmware, you lose the jailbreak ability on your device until iPhone Dev Team updates its existing jailbreak tools or develops a new tool to jailbreak that specific firmware.
The same case is with iOS 4.3.4 firmware. If you install iOS 4.3.4 on your device, you will lose the jailbreak ability. Now all you can do is either to wait for a new jailbreak, which might take a long time to come, or to downgrade to previous iOS firmware which is only possible if you have already saved the SHSH blobs for the firmware to which you are downgrading. But if you have not saved the blobs and want to keep your device jailbroken, you are advised to use the below mentioned simple trick that prevents iTunes from showing any update message. This trick will make iTunes to think that your device is running on iOS 4.3.4.
Step 1: Download iFile from Cydia Store.
Step 2: Go into System/Library/CoreServices/SystemVersion.plist and open the file in Text Viewer.
Step 3: Tap on Edit button present on top left side.
Step 4: Change 4.3.3 to 4.3.4 and 8J2 to 8K2 and tap on Save button.
Step 5: Reboot your device.
Now connect your device with iTunes and you won’t receive any update warnings.