SilentSilo от Software Hive S.R.L.

SilentSilo fills your saved logins into web pages. It works with the SilentSilo desktop app on Windows, version 1.2.0 or later, running on the same computer. Without the desktop app the extension cannot fill anything.

How a fill works
1. On a login page, click the SilentSilo button in the toolbar.
2. The extension asks the desktop app which logins are saved for this site and shows their names and usernames.
3. You pick one. The desktop app shows a confirmation naming the site and the login, and you confirm with Windows Hello or your security key.
4. Only then does the app send the username and password, and the extension writes them into the two fields on the page.

What the extension keeps
Nothing. It holds no key and no copy of your logins. It does not store the username or password it fills, and it sends them only into the page you clicked on. Your silo is unlocked in the desktop app, not in the browser.

Matching by site
A login is offered on the site it was saved for: the same address, with or without "www.". A look-alike address matches nothing, and the popup warns that the page may not be the site you think. You can still search all your logins on purpose; the desktop app then tells you that the login was saved for another site before you confirm.

What it asks Firefox for
- Native messaging, to talk to the SilentSilo desktop app on this computer.
- Active tab and scripting, to write into the tab you clicked the button on, only then, and only in its main frame.
No access to all sites, no script that runs on every page, no storage, no network requests.

Before you start
- Install SilentSilo for Windows from silentsilo.com and open your silo.
- In SilentSilo, turn on Settings > Browser extension.
- Set up Windows Hello or a security key for the silo under Unlocking. Every fill is confirmed with one of them.

Not in this version
Saving new logins from a page, filling cards or addresses, filling forms inside frames, Firefox for Android, and macOS or Linux.

Open source
The extension and the desktop app are open source under the AGPL-3.0: github.com/silentsilo/browser and github.com/silentsilo/desktop.