So recently people finally figured out that the iOS 6.1.3 OTA Signing window is still open for some devices. I will proceed to explain about why and what this means. OTA Update (via iPhoneWiki) OTA Updates (Over-the-Air Updates, also know as wireless updates) were introduced with iOS 5. This allows a user of a device to go into Settings > General > Software Update and download and install the latest iOS software on-device, without the need for iTunes. The device contacts mesu.apple.com to check for updates. The updates are delivered in plain unencrypted ZIP files. The Open iOS 6.1.3 OTA TSS Signing Window This windows is open for the following devices iPhone 4S iPad 2 According to when I asked Xander, this window is open for in case a device new in box has iOS 5.0/5.0.1 because a direct update to iOS 8.1.3 is probably too risky and apple prefers not to run risks. I asked iH8sn0w also, he said he doesn't know but did considered what is said above. Can it be exploited? Yes, but not easily nor any method is known. I asked iH8sn0w privately about it. He did reply with a vague answer and told me not to share what he said. But this would only work on the iPhone 4S and iPad 2. All private messages asking me about what he said will be ignored. "My iPhone 4 is on iOS 5.0.1. Can I update to iOS 6.1.3 with this?" No. The TSS Window is not open for the iPhone 4. Here is a table list of the devices that have an open TSS Window for iOS 6.1.3 iOS Device is it open iPhone 3GS no iPhone 4 no iPhone 4S yes iPhone 5 no iPad 2 yes iPad 3 no iPad 4 no iPad Mini no iPod Touch 4 no iPod Touch 5 no Apple TV yeah? This means if you downgrade your iPhone 4 or iPod 4, it won't get the iOS 6.1.3 OTA. No need to try. It won't happen. Can you OTA a Tethered Downgraded iPhone or iPod? Yeah. Feel free to try. It will work. Feel free to ask me a question via iMessage (PM me for iMessage), on this post, or contact me via Twitter.