Updated Feb. 6 with more details of the update and the unusual way to upgrade to it.When Apple released the most recent iPhone software update, iOS 18.3, it was for every iPhone from the iPhone XS onwards. You can read comprehensive details of whats in it here, and whether you should upgrade to it here. Now, Apple has re-released the software with a new build number, for three iPhones only: iPhone 11, iPhone 11 Pro and iPhone 11 Pro Max. Whats more, to install it, you have to sideload it: you cant just do it the usual way by opening the Settings app, and choosing Software Update.Three Apple iPhones have just been updated again. Getty ImagesIts available for the iPhone 11, iPhone 11 Pro and iPhone 11 Pro Max only at this time. If you want to install it, you have to use a Mac or Windows computer, plug in your device and install it that way through the finder by clicking update, according to Aaron Zollo at YouTube channel Zollotech.Zollotech also says that even if youre updating from earlier software and you choose the over-the-air solution, youll still get the earlier build, not the new one.Apple still hasnt given any details of why the iPhone 11 series is getting this extra version, but a bug issue seems the most likely reason. Some users on Reddit have variously referred to reports of Safari breaking and Mail issues, but neither has been confirmed by Apple.MORE FOR YOUThe original update was released on Monday, Jan. 27 with build number 22D63. But on Monday, Feb. 3, Apple released iOS 18.3 with a new build number, 22D64. You wouldnt need to know this unless you have one of the iPhone 11 series handsets, first released in fall 2019. If you do, and you go to the Settings app and choose Software Update, youll find the option to update to the new version.As to whats in it, Apple hasnt gone into detail. We know whats not in it: the many Apple Intelligence changes that iOS 18.3 brought to the most recent iPhones. Only the iPhone 15 Pro, Pro Max and iPhone 16 series are compatible with Apple Intelligence.So, the new version most likely is there to fix something that didnt quite take in the first release, something that only the iPhone 11 series somehow continued to find a problem.The notes only point to issues other iPhones have seen fixed in the latest update, that is, these three things. First, the Calculator app now repeats the last mathematical operation when you tap the equals sign, something which it used to do before, and now can again. Second, it fixes an issue where the keyboard might disappear when initiating a typed Siri request. And third, the update Resolves an issue where audio playback continues until the song ends, even after closing Apple Music. Sucha weird one, that.If you have an iPhone 11 series, even if you upgraded to iOS 18.3 already, Apple is recommending you install this new version. As the similarity of build numbers suggests, its very close to the last one, only this time itll fix things, lets hope.