Troubleshooting Firefox: Security Key errors caused by First-Party Isolation (FPI)

Firefox Security Key Issue: First-Party Isolation (FPI)

When using the First-Party Isolation (FPI) setting in Firefox (privacy.firstparty.isolate=true), the authentication process may fail to recognize your physical security key. This specific browser configuration prevents the verification prompt from communicating effectively with external hardware.

This issue affects U2F and FIDO devices, including:

• YubiKeys
• Trezor keys
• Other hardware security tokens

How to Resolve

To log in using your security key, you must disable FPI within your Firefox configuration:

1. Type about:config in your Firefox address bar and press Enter.
2. Search for privacy.firstparty.isolate.
3. Set the value to false.

Alternative Methods

If you prefer to keep First-Party Isolation enabled for privacy reasons, you can still access your account by using a different verification method, such as:

• Push notifications via the mobile app.
• Passcodes generated by the mobile app or a hardware token.

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See also: KB0015275 - Recommended Browsers for CalNet Services