How safe and necessary is this update?

Is the update "necessary"?

Yes and No

Yes, if you want to have the most up to date security on your phone.

No, if you don't.

But, it's your call. You can skip this one if you want, but it will be built in to the next one that will appear soon.

Is the update "safe"?

Many millions of users have already updated. I have yet to see anyone on this support forum reporting a problem. But, someone will at some point......like the guy with an old phone who is trying to update using a cellular connection reporting that he has "tried everything".

Let's start with anytime you update the version of iOS on your iPhone, you should back it up ... either to iCloud or to a computer BEFORE applying the update.

With that said, any update has the risk that may require that you will need to restore the phone. That process will completely erase it, and why you will want those backups should this be the case.

As far as necessary ... Apple has made the decision, based on whatever processes they use, that this was a significant security issue to be addressed, and required an update to their operating system. Apple is not alone in making these type security updates so they shouldn't come as a surprise to anyone these days.

However, whether or not, you will want to install the update is totally up to you. Just be aware, it may very well be included in a future update anyway.

Very safe and fixes a flaw being actively exploited by hackers. You should update ASAP.