I'm not sure about the former, but the answer to your second question is yes, they do client-side encryption: https://support.mozilla.org/en-US/kb/how-firefox-s

I'm not sure about the former, but the answer to your second question is yes, they do client-side encryption: https://support.mozilla.org/en-US/kb/how-firefox-sync-keeps-your-data-safe-even-if-tls-fails https://support.mozilla.org/en-US/kb/how-firefox-sync-keeps-...