Firefox 43 now requires that extension publishers have their extensions reviewed and signed by the Mozilla Add-ons team. This article has more information: Add-on signing in Firefox.

Since some publishers have not completed this process, you can make a temporary exception to the signing requirement until they get updated. This is global for all extensions, there's currently no way to only make an exception for one specific extension.

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste xpin and pause while the list is filtered

(3) Double-click the xpinstall.signatures.required preference to switch it from true to false -- note that this is for Firefox 43 only, it is already false in Firefox 42, and it will no longer work in Firefox 44 (unless something changes)

Thanks for the answer, but a solution only for version 43 is no solution at all. I have also posted the problem in the Adobe Community. I still don't understand how Firefox 43 crashes Acrobat 11 Pro (11.0.13.17) when it executes a tool that has nothing to do with the browser/internet (the batch OCR of tif files stored on HD) . I have no alternative to do ClearScan OCR other than with Adobe Acrobat.

Hi lingneru, I can't think of any reason Adobe would crash when it is executing an internal function and Firefox is not even running. Maybe something else updated around the same time?

lingneru said

... The issue with Adobe Acrobat happens even with Firefox closed ... If there is no solution, I must look for another browser.

Is Firefox crashing, too? If so, see this - Troubleshoot Firefox crashes (closing or quitting unexpectedly)

If that Adobe application is crashing even when Firefox isn't running, why would you think that Firefox was even a partial cause of the crash? The timing of when that started happening is probably coincidental with the Firefox 43 update, if the crashes happen when Firefox is closed.

Overall, it isn't an "either or" thing with web browsers, you can have as many different web browser applications installed, and you can usually even use them at the same time; although only one can be set as the "default browser".

Dears, thanks for your attention.

I installed Firefox 43 again - it's version 43.0.2. Before installing, I disabled Avira Real Time Protection. Unfortunately the problem persists. Attached a jpg screenshot what I get just when Acrobat crashes. When I reinstall Firefox 42 the problem is solved. Firefox is my default browser, never use IE and others aren't installed. In my Revo application list Firefox 32-bit is shown, although my system is Win 7 Pro 64-bit. Firefox is on the OS partition; Adobe Acrobat/Adobe Reader/Adobe Elements, Foxit and some other programs are on a separate partition. I use this the last 10 years or so and never had problems. I already have tried an Acrobat repair, with no effect. What I can do more is send you a log file - but what? The attached gif has the Windows log info of the event. Other thoughts: is Firefox portable? Never tried to run it on a pen drive. Best regards

It looks as though Acrobat is checking the status of its Firefox extension while you are trying to OCR a document. If you see that in the future -- for example, when reading a document -- try clicking the Do Not Tell Me Again link on that little panel.

I tried it, didn't help. I reinstalled Firefox 42 and all works nice again. My system is new - from November 1st. 2015, but last updated Nov. 8th. But I now see another problem - with Acrobat's file extension disabled, I probably cannot convert web pages to pdf. I suggest we gave up; for now I will stay with Firefox 42 for about 6 months to see if something changes - maybe an Adobe update. Best Regards

Ulrich Lingner

You can allow unsigned/unverified extensions in Firefox 43, but I doubt that is related to the crashing.

For security reasons, you should not stick with old versions of Firefox. But that's a discussion for another day.