I can access about:addons just fine with uBlock Origin installed on all versions of Firefox currently being offered (Fx, FxBeta FxDevEdition, FxNightly)

You mention that it works in safe mode. I see a add-on labeled FF AntiVirus Check 9.0.0 ({4cbef3f0-4205-4165-8871-2844f9737602}) . I can't find that on AMO so its probably malicious and the reason why you are unable to access the add-ons page. Try doing a refresh to get rid of it but before doing so, go into your profile folder (about:support --> Profile directory --> Open Folder --> Extensions. Find and delete any entry of FF AntiVirus Check or its UUID (4cbef3f0-4205-4165-8871-2844f9737602})

he Refresh feature (called "Reset" in older Firefox versions) can fix many issues by restoring Firefox to its factory default state while saving your bookmarks, history, passwords, cookies, and other essential information.

Note: When you use this feature, you will lose any extensions, toolbar customizations, and some preferences. See the Refresh Firefox - reset add-ons and settings article for more information.

To Refresh Firefox:

1. Open the Troubleshooting Information page using one of these methods:
   • Click the menu button , click help and select Troubleshooting Information. A new tab containing your troubleshooting information should open.
   • If you're unable to access the Help menu, type about:support in your address bar to bring up the Troubleshooting Information page.
2. At the top right corner of the page, you should see a button that says "Refresh Firefox" ("Reset Firefox" in older Firefox versions). Click on it.
3. Firefox will close. After the refresh process is completed, Firefox will show a window with the information that is imported.
4. Click Finish and Firefox will reopen.

I have NoScript and haven't noticed any problems like that.

Not that you want malware lingering on your system, but if you could "quarantine" the questionable extension to a separate folder (I have a folder in my Downloads called VIRUS where I put questionable things) then later someone might request a copy to analyze.

Thanks, it was indeed the FF AntiVirus Check 9.0.0 add-on that was creating a conflict, (pretty sure it was some type of adware/malware), though i can't show it now, it was a very very convincing page that prompt you to download (every single detail of Mozilla Firefox appearance was mimic perfectly), something Mozilla should check it out, and ban it.

In my case, it was FF Tool AdBlock 1.9.9 add-on that was creating a conflict, something Mozilla should check it out, and ban it.

Hi eeerrr, that sounds like one of those extensions which installs from the fake update page that can take over your screen. Since they are not distributed through the Mozilla Add-ons site, I think they do not get the same level of review. Do you recall where you got it from? I'm not sure of the best way to discover that; possibly a suspicious site in your history? (Not that you want to go back!)

There was a fake "FF Safe Helper" extension installed by a fake manual Firefox update scam that Mozilla blocked on January 8. One of the things this extension did was auto-closes about:addons as soon as it is opened.

https://blocked.cdn.mozilla.net/674b6e19-f087-4706-a91d-1e723ed6f79e.html https://addons.mozilla.org/blocked/

Btw the official abbreviation that Mozilla uses for Firefox is Fx and not the FF that many newer Firefox users may use.