The SilentSilo extension works only with the SilentSilo desktop app on the same computer. When you click its button, it sends the current tab's address to that app to find the logins saved for the site. When you confirm a fill in the app, it receives one username and password from the app and writes them into the page. It does not store either, and it sends nothing to SilentSilo or to anyone else. It has no analytics and makes no network requests. Full policy: https://silentsilo.com/privacy/#browser-extension