Firefox unable to install extensions

[alanlivio]

Windows Version

Microsoft Windows [Version 10.0.26100.4349]

WSL Version

2.5.9.0

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

6.6.87.2-microsoft-standard-WSL2

Distro Version

Ubuntu 24.04

Other Software

This is a follow up of #2353. See steps below

20250623-1809-13.0556545.mp4

Repro Steps

Open WSL -> Open Firefox -> Install one Extension -> Install does not happen.
See steps below

20250623-1809-13.0556545.mp4

Expected Behavior

install extension

Actual Behavior

exntesion is not installed

Diagnostic Logs

WslLogs-2025-11-19_17-58-37.zip

[github-actions]

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Invoke-WebRequest -UseBasicParsing "https://raw.githubusercontent.com/microsoft/WSL/master/diagnostics/collect-wsl-logs.ps1" -OutFile collect-wsl-logs.ps1
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[BHH01]

I just faced this problem today myself. I would also add that - for me - installing the addons/extensions is possible if I start Firefox as an administrator ("sudo firefox") from command line, that could give a hint to the underlying problem for the ones in the know.

UPDATE: I've found the workaround! As it's stuck when one tries to click on the "Add" button, using the "ALT+A" key combination instead allows the installation process to continue, and "voilà"!

[sirredbeard]

Did you install Firefox via Snap or apt?

[alanlivio]

hi @sirredbeard. I install by sudo apt install firefox. But seems that internally ubuntu call snap. See my apt list

$ apt list firefox
Listing... Done
firefox/noble,now 1:1snap1-0ubuntu5 amd64 [installed]

[sirredbeard]

I would be interested to see if you could reproduce it with the apt package directly from Mozilla. Here is an article on how to do so.

If it does not affect the apt package method, we can escalate to the snap team at Canonical.

[benfishbus]

I encountered this on Ubuntu the same as the original poster. So I switched over to Debian and added Mozilla's package repository (per this guide) and installed firefox from there. Same behavior.

• Launching firefox from its WSL app shortcut or from the WSL command line as regular user = can't add extensions. Specifically, clicking the Add button does nothing (as does Alt+A).
• Clicking Cancel also does nothing. I have to close the tab to get rid of the install dialog.
• sudo firefox installs extensions just fine.

[Mooninaut]

I found a strange workaround, which is to right-click inside the "allow in private windows" checkbox, choose "Select All" which then gives keyboard focus to the dialog, then tab focus to the "Add" button and press space.

Pressing Alt-A did not work for me.

[cxsxrrrr]

I resolved the issue with Firefox addons on Kali Linux using two distinct solutions:

Solution 1: Executing Firefox using the sudo command as @BHH01 said.

Solution 2: Utilizing the Win-Kex environment.

Both solutions worked for me individually.

[github-actions]

Diagnostic information

Issue was edited and new log file was found: https://github.com/user-attachments/files/23634660/WslLogs-2025-11-19_17-58-37.zip
Detected appx version: 2.5.9.0

[samymohammed]

another workaround is to keep holding the ctrl key when clicking add extension button (before the popup shows until the add key is clicked)

[AntoineBLUNTZ]

another workaround is to keep holding the ctrl key when clicking add extension button (before the popup shows until the add key is clicked)

Your workaround worked for me on Thunderbird (installed via WLS), when trying to add language packs.
Thank you!