I actually noticed some weird and potentially concerning behavior with Firefox Quantum this morning.

I had a fair number of tabs open (~28 or so), and I restarted the browser so a change I made would take effect. I have FF set to show my windows and tabs from my previous session on start up, but it instead launched with a single tab showing my home page. Okay, no big deal, I'll just restore my previous session from the History menu. When I clicked on the history menu, though, I didn't see my most recent history, but instead a list of URLs from my bank.

I assume this is due to a syncing issue with my Firefox account (I changed my banking password just to be safe), but it's still concerning.