Many iPhone owners are wondering whether they should follow the iTunes prompt and update to iOS 4.3.4 or not. There are a few questions you might ask yourself before making this decision to help determine if the 4.3.4 (4.2.9 on Verizon) firmware update is for you. Skipping the update leaves your device at iOS 4.3.3 or earlier, which could be useful down the line.
First it's important to understand what Apple is trying to accomplish with the iOS 4.3.4 update. The primary purpose is to fix a PDF security vulnerability on your iPhone. This may sound bad, but read on for more details. This vulnerability is the same weakness that makes the remarkably easy and fast JailbreakMe 3.0 procedure possible.
So the main question is: have you already jailbroken, or are you potentially interested in jailbreaking your iPhone? If the answer is "absolutely not, I will never jailbreak, root or otherwise hack my iPhone ever" then by all means update to iOS 4.3.4. If you plan to jailbreak then do not update to iOS 4.3.4 as this will complicate your life and make an untethered jailbreak impossible for the time being.
But what about the security vulnerability? Of course you don't want some arbitrary code messing up your iPhone if you happen to read a maliciously crafted PDF file. Paranoid types will entirely avoid opening PDF files on their iPhone, but this solution is limited as you could easily open a PDF in the web browser unknowingly. Get this: the way to protect yourself and preserve the ability to jailbreak your iPhone is to jailbreak your iPhone!Developer comex has already released a patch in the Cydia jailbreak app store to fix the PDF vulnerability. So after you jailbreak using JailbreakMe 3.0 the PDF issue can be resolved immediately by installing PDF Patcher 2. For those interested in jailbreaking this solution should alleviate any worries about missing the security patch found in iOS 4.3.4 and 4.2.9.