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Get error "Out-of-process WebExtensions are not supported with multiple child processes" in log when installing some addons

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  • Last reply by cor-el

Nawor3565
Nawor3565
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I recently updated to Firefox 56.0. I was using uBlock Origin before the update, and it worked fine, but after updating the addon disappeared from the addons area and didn't function, and a reinstall didn't help. I did some digging and it looks like the latest version of the addon that works is 1.13.8, the last version without WebExt. I tried installing the addon both in FF Safe Mode and in a different Windows profile with a refreshed FF. Installing in Safe Mode didn't work, same problem. But installing with the refreshed FF worked fine, even though I was using the same uBO and FF versions.

I looked at the browser logs when I installed the addon both times, here's the log for the refreshed FF: https://pastebin.com/hNDcrY97 and the one for my normal FF: https://pastebin.com/h0CFTPZD

It looks like the problem is "Error: Out-of-process WebExtensions are not supported with multiple child processes." I did discuss this with the head developer, but they couldn't recreate it on their end so there's not much they can do. In about:config, "extensions.webextensions.remote" is set to true. I'd like to only refresh my FF profile as a last resort, since I have a lot of addons/other custom settings that would be a pain to restore. Is there anything else I can try to track down the cause/solution to the error? Thanks for your help!

I recently updated to Firefox 56.0. I was using uBlock Origin before the update, and it worked fine, but after updating the addon disappeared from the addons area and didn't function, and a reinstall didn't help. I did some digging and it looks like the latest version of the addon that works is 1.13.8, the last version without WebExt. I tried installing the addon both in FF Safe Mode and in a different Windows profile with a refreshed FF. Installing in Safe Mode didn't work, same problem. But installing with the refreshed FF worked fine, even though I was using the same uBO and FF versions. I looked at the browser logs when I installed the addon both times, here's the log for the refreshed FF: https://pastebin.com/hNDcrY97 and the one for my normal FF: https://pastebin.com/h0CFTPZD It looks like the problem is "Error: Out-of-process WebExtensions are not supported with multiple child processes." I did discuss this with the head developer, but they couldn't recreate it on their end so there's not much they can do. In about:config, "extensions.webextensions.remote" is set to true. I'd like to only refresh my FF profile as a last resort, since I have a lot of addons/other custom settings that would be a pain to restore. Is there anything else I can try to track down the cause/solution to the error? Thanks for your help!
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Modified by Nawor3565

Chosen solution

You can still give a clean profile a try.

You can create a new profile to test if your current profile is causing the problem.

See "Creating a profile":

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

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cor-el
cor-el
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Chosen Solution

You can still give a clean profile a try.

You can create a new profile to test if your current profile is causing the problem.

See "Creating a profile":

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.