Huh? An Apple iPhone jpeg file is "not from an authorized developer?"

Unfortunately, I have not been able to find that topic. It was a couple of years back now. The forum search function has been massively broken for well over a year, and I couldn't locate if via Google.

But as a guess, it may be the Launch Services database is damaged. The Mac uses this to keep track of what file types belong to what apps. It used to be more work to reset this. But, if I remember correctly, it's now just a file in the Preferences folder of your account with a very obvious name. Pretty sure it's LaunchServices.

All you have to do is shut down all running apps, put the file from your Preferences folder in the trash and restart. A new database will be built.

It's a fault in the OS that shouldn't be happening. It thinks an image is a program. Clearly wrong.

I've seen a few other topics like this where the OS was incorrectly treating one file type or another is if it were an app. Problem is, I don't recall what the fix was.

Now that I'm back on my Mac, I can look instead of guessing/trying to remember. The items in the user account Preferences folder are these two:

com.apple.LaunchServices (a subfolder)

com.apple.LaunchServices.QuarantineEventsV2

But there are far more items on the drive with LaunchServices as part of the name, including within the hidden /var folder.

There is a way to do it from Terminal, but the command changes from one OS to another. The easiest way to do this, by far, is to use the free utility, OnyX. Make sure to download the version of OnyX that matches the version of macOS you're using.

As shown next, go to the second tab and uncheck everything except LaunchServices, and then click the Run Tasks button.

This will reset everything, including any manual changes you made with Get Info. Such as changing PDFs to open in Acrobat rather than Preview.

You're welcome. 🙂

Has the air dropped photo been edited with third-party photo editing extensions?

Third-party apps can embed malicious code into files that look like a harmless JPEG but are no longer JPEG.

You may want to check the Info ⌘i for the downloaded JPEG and look at the "Open with" line in the Info panel, if it is still set to Preview. If not, try to change this to Preview.