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Addon could not be installed because Firefox/LibreWolf cannot modify the needed file.

  • 5 replies
  • 0 have this problem
  • 28 views
  • Last reply by Auberonn
  • Archived

Auberonn
Auberonn

I can't figure this out. I've been having this issue ever since I deleted my KMspico files after I did a scan using Malware Bytes (it was labelled as dangerous files or whatever so I let the app delete it).

After the restart, I can't use nor reinstall the Discord app along with being unable to download any Extensions, Themes, or Plugins for both Firefox and LibreWolf. It's frustrating as I had to go back to previous browsers, which I didn't want to do. Any help in fixing this is highly appreciated as I really want this fixed.

--- File location is C:\Program Files (x86)\LibreWolf [Same for Firefox]

--- Must I reinstall Windows in order to fix this issue or are there other ways that don't involve reinstalling Windows?

I can't figure this out. I've been having this issue ever since I deleted my KMspico files after I did a scan using Malware Bytes (it was labelled as dangerous files or whatever so I let the app delete it). After the restart, I can't use nor reinstall the Discord app along with being unable to download any Extensions, Themes, or Plugins for both Firefox and LibreWolf. It's frustrating as I had to go back to previous browsers, which I didn't want to do. Any help in fixing this is highly appreciated as I really want this fixed. --- File location is C:\Program Files (x86)\LibreWolf [Same for Firefox] --- Must I reinstall Windows in order to fix this issue or are there other ways that don't involve reinstalling Windows?
Attached screenshots

All Replies (5)

markwarner22
markwarner22

You should contact Librewolf about Addon installation issues.

jscher2000 - Support Volunteer
jscher2000 - Support Volunteer

What version is Librewolf based on?

There is a general issue with versions of Firefox older than 128.0, with the exception of the Extended Support Release of Firefox 115, 115.13.0esr or later. If this issue started Friday, I would investigate that first:

Update Firefox to prevent add-ons issues from root certificate expiration

Auberonn
Auberonn Question owner

The version I have for LibreWolf is 136.0.1-1 and this issue did not start on Friday. Unfortunately, I don't remember exactly when this happened but this situation of mine started sometime in the last quarter of 2024.

jscher2000 - Support Volunteer
jscher2000 - Support Volunteer

When I search for the "cannot modify needed file" message, I mostly find quite old threads like this one:

https://support.mozilla.org/questions/1183622

It sounds like that was for XUL add-ons (pre-Firefox 57 add-ons).

But setting aside the peculiarities of the older versions, could it refer to a problem with disk permissions? Have you tried a new profile? Profile Manager - Create, remove or switch Firefox profiles.

Auberonn
Auberonn Question owner

I created a new local account for my PC not too long ago and tried to see if LibreWolf was able to download extensions and themes. Surprisingly, it worked! (Along with the discord download issue) but I want to solve this on my main administrator account.

Any ideas on this end or should I move over to a Microsoft forum instead?