One needs to download
OWP.Communicator.exe for the add-on to work. All right no pb.
You start OWP.exe and it tells you there's another version. All right... I download the latest one.
You start OWP.exe and it tells you .... there's another version. And so on and so on.

OWP.Communicator.exe does NOTHING more than opening a pop-up message "New version available". You can download it 10 times it won't change a thing. Nothing works. Useless crap.

Квк вариант, взамен этого неработающего дополнения можно использовать Open in GIMP photo editorот Andy Portmen
https://addons.mozilla.org/ru/firefox/addon/open-in-gimp
И в настройках указать путь к своему редактору. Например: C:\Program Files\Adobe\Adobe Photoshop 2020\Photoshop.exe

Does not work.

Only Download the image but not open in Photoshop. Useless

Does not work with Firefox Quantum. Right-clicking an image downloads the image to the downloads folder (Mac), but doesn't open the file in Photoshop. This app used to be really helpful.

BarisDerin (or whatever his name is) had an addon extension for a long time that worked. The only issue was when Firefox was updated, and there was a wait for the addon to be updated to run on the updated Firefox.
Now, it seems that BarisDerin is pimping for Google, as his Open With Photoshop extension only seems to work with Chrome. (I haven't even tried it, because I am a Firefox user, period.
I don't know if the same developer is responsible for this useless piece of crap. IT DOES NOT WORK WITH FIREFOX QUANTUM 57 as claimed, nor with any earlier version of Firefox.
What kind of QC does Mozilla have to allow crap like this to be listed on their Extensions page?
Get a grip. Fix it!

It just goes to this page: http://barisderin.com/extension/openwithps/options.html
And then downloads the image when I press it again after. Doesn't open Photoshop