Apple 15.2.1, the sixth update to the major release of iOS 15 in September, is here. You may have seen a prompt on your phone to upgrade your operating system, but if not, you can check by going into Settings, General and then Software Update. The upgrade is free and available on all eligible devices (iPhone S and later) over the air. Compared to the earlier 15.2 update, it is a relatively small one that addresses an issue causing Messages sent through an iCloud Link not to load and it fixes a bug with third-party CarPlay apps not responding to input. Should you download it? In a word, yes.

Even if the fixes do not apply to your usage, you should still update the OS. Why? Because it also addresses a security issue wherein “a maliciously crafted HomeKit accessory name may cause a denial of service,” Apple said in a note for the release on its security support page. If that sounds a bit vague, and it did to me, it’s worth a closer look.

In August, a security researcher discovered a vulnerability in iOS 14.7 and later that could crash affected devices. It worked through default settings for HomeKit, Apple’s framework inside its Home app to find, connect and control smart home devices such as security cameras, doorbells, outlets and light bulbs. A hacker could take advantage of this problem in the software by sending a Home device invitation that would trigger the user’s Home app and phone to crash. If the user restores the device and signs back into his or her iCloud account, the Home app will once again become unusable and the phone may become inoperable, resulting in a restore and crash loop. If you were out of town, that could cause real problems with your connected smart devices.

You should know that no problems have yet to be reported with the update, which is one thing we do want to check before updating an operating system or an app. However, security fixes should take priority over most other issues.

It’s important to note that fixes are cumulative. If you didn’t update the iOS on your compatible device when 15 came out, now is the time to catch up. And if you’re running iOS 14, you can no longer update it with security patches despite Apple previously saying it would continue to support it. In December, these security updates were no longer available. Your only option is the most current version, iOS 15.2.1. Set aside some time for the update. The further behind you are, the more data there is to download for the upgrade.

Gottobemobile posted a helpful table showing the various tasks involved in updating to the new iOS along with estimated times for each. Syncing your devices can take from five to 45 minutes, backup and transfer (essential, do not skip the backup even though it’s optional) from one to 30 minutes, download from minutes to an hour, and installation from seven to 15 minutes. So if you’re running 15.2, your total time could be as short as 12 minutes, and if you’re significantly behind, you could be looking at as long as 2 ½ hours. You’ll want to keep an eye on your phone as it runs through the process to catch any holdups or issues. Be sure to plug your phone into a power source before starting. Try to schedule the download when there’s nothing else running on your Wi-Fi and at a time that’s less busy. In other words, not right after school gets out.

Once you’re finished, you can feel secure that you have the latest privacy and security updates available for your iPhone. You may also find that some of your older apps need updating too to be able to run on the current system. For those still using iOS 12 or older, you won’t find the updates tab in Apps anymore. Apple changed its placement and users now update their apps from the account section inside the App Store. In the App Store, tap your profile picture at the top right. Scroll down to see which of your apps have updates available. You can update them one-by-one or select Update All.

Leslie Meredith has been writing about technology for more than a decade. As a mom of four, value, usefulness and online safety take priority. Have a question? Email Leslie at asklesliemeredith@gmail.com.

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