I very briefly logged into the Firefox browser on a shared work PC using my personal account. I immediately logged back out again, and even checked to make sure it was not remembering my email/suggesting it for future sign-ins. The next day when I went on Firefox on this PC, it was not signed in (on the top right settings bar it said "sign in" rather than showing my email, and clicking this brought me to the sign on page) but it was still showing my shortcuts and all my bookmarks. Having gone onto my usual laptop, it's also synced the bookmarks that were on this work PC (with no account associated) to my personal account. It's like it's synced them entirely even though I never pressed sync, was only signed in for a minute and signed out fully afterwards. This is a huge privacy breach for me, since it means my personal information contained in the bookmarks was on display for the dozen people who used that PC before I noticed what had happened. I deleted all the bookmarks on this PC, cleared cache and cookies completely and it did not seem to be showing anything anymore, but I'm not confident it's scrubbed permanently since it never should have been showing those things in the first place. I realise I'm just going to be told I must not have signed out properly, but I really did. I'm paranoid about these things and I clearly remember doing it. Surely if I sign out, my personal things like bookmarks should not be available to anyone using Firefox on that PC in the future? I'm struggling to understand why this happened and how to keep my account safe now.