Passcode Requirement: You must change your iPhone unlock passcode within 60 minutes.

Issue:

A couple of weeks ago, after unlocking my iPhone I received a strange prompt on my iPhone 5 (running iOS 9.3.1, not jailbroken) saying that I had to change my passcode within 60 minutes.

Not thinking much of it, I followed the instruction and changed the passcode via the prompt. I didn't think to question the fact it didn't give me any options other than to pick a 4-digit passcode.

After changing it, I was again 2 weeks later (2 days ago as of writing this) prompted to change my passcode, except this time I had 58 minutes to do this.

I found this to be a bit fishy so I researched it and there was no apple documentation on it, only forums of a lot of other iPhone users that had experienced the same thing and the forums were dated as far back as 2012 (that I saw anyway, could have been more before that too).

I rang apple support, and they weren't aware of this issue as there wasn't a feature for iOS that made this happen and recommended I immediately reset my settings (by going to Settings > General > Reset > Reset All Settings). This resets all settings, doesn't erase any of your data.

It was my personal guess that if it was in fact malicious software, it may be connected to the operating system some how because the first time I changed my passcode via the prompt and it worked. So I made the decision to backup everything I wanted to keep manually, and not via iTunes and then manually get everything back. This may have been unnecessary but again it was my guess that any recent iTunes backups I had may have had this issue.

If it was in fact malicious, I'm not sure what kind of access it could of had to my phone, be it data or whatever. I may be slightly paranoid but wanted to remain on the safe side as pretty much everything I have was set up and connected to my phone. So I went the full length and changed a lot of the settings for accounts I have. Again, probably wasn't necessary but being safe.

So if you experience this yourself, just know that it isn't created by apple and you should at least reset your settings.

Hope this clears anything up!

P.S. This isn't a screenshot I took, it is one I found on another stackexchange thread (source: http://apple.stackexchange.com/questions/124771/is-the-message-you-must-change-y our-passcode-within-60-minutes-valid-non…). Although it is exactly was I got