This extension's data handling is described in the Field privacy policy, under the "Browser extension" section: https://getfield.net/privacy

In short: the extension communicates only with the Field server you sign in to (getfield.net by default, or a self-hosted instance). It sends your email/password to that server at login, stores the session token locally in the browser, and uploads the images/text/links you explicitly choose to save along with the source page URL. No data is sent to any third party; there is no tracking or analytics.