Downgrade LastPass Firefox extension to a specific version

downgrade-lastpass-firefox.md

Fix: LastPass Causes Firefox to Freeze on Passkey / YubiKey Login (Gmail, YouTube, Google)

LastPass extension versions newer than 4.145.0 can cause Firefox to freeze, hang, or become unresponsive when performing:

• Passkey authentication
• YubiKey / FIDO2 / WebAuthn security key login
• Google account login (Gmail, YouTube, Google Workspace, etc.)

Widely reported issue affecting many users. The browser becomes completely unresponsive and must be force-quit.

Keywords: LastPass Firefox freezing, Firefox hangs on YubiKey, Firefox stuck on passkey prompt, LastPass WebAuthn freeze, Firefox Developer Edition LastPass bug, security key not working Firefox LastPass

Solution: Downgrade LastPass to v4.145.0

1. Download the working version

curl -L -o /tmp/lastpass-4.145.0.xpi \
  "https://addons.mozilla.org/firefox/downloads/file/4535188/lastpass_password_manager-4.145.0.xpi"

2. Install in Firefox

Firefox Developer Edition (macOS):

open -a "Firefox Developer Edition" /tmp/lastpass-4.145.0.xpi

Regular Firefox (macOS):

open -a Firefox /tmp/lastpass-4.145.0.xpi

Any OS: Navigate to about:addons, click the gear icon, select "Install Add-on From File...", and choose the downloaded .xpi file.

3. Click "Add" in the installation prompt

4. Disable auto-updates

Prevent Firefox from upgrading LastPass back to the broken version:

1. Go to about:addons
2. Find LastPass → click the three-dot / gear icon
3. Select "Turn Off Automatic Updates"

Affected Versions

• Broken: LastPass versions newer than 4.145.0
• Working: LastPass v4.145.0 and older
• Browsers affected: Firefox, Firefox Developer Edition, Firefox ESR