Hmm, I don't think that is from Sync, but maybe from Firefox's built-in password manager? Try turning that off here: "3-bar" menu button (or Tools menu) > Options > Security Uncheck the box for "Remember passwords for sites" Does that get rid of the prompts? If not, could you post a screen shot of the prompt you're getting? This article has tips on capturing that: [[How do I create a screenshot of my problem?]] Please delete or obscure any personal information before posting. (There is a Browse... button below the text box to attach the image.)