The SecretSafe browser extension does not completely function in Firefox's private browsing mode. This is a known issue specific only to Firefox. You will see a message indicating so when you try to open the SecretSafe popup window in a private window. We have discussed the problem with Mozilla, however, they seem unable to fix it so that extensions like SecretSafe can function entirely in private mode.
As a workaround, if you are looking to auto-fill a login while in a private window you can use the right-click context menu:
- Navigate to the website's login page while browsing in a private window.
- Right click the page. A context menu will appear.
- Select SecretSafe → Auto-fill and then pick your login.
Alternatively, you can also copy/paste your login credentials by accessing your safe in the popup from a regular, non-private browsing window.
- GitHub discussion: https://github.com/secretsafe/browser/issues/136
- Firefox Bugzilla report: https://bugzilla.mozilla.org/show_bug.cgi?id=1329304