I also just had this happen as well and have the same setup. Unique password stored in keepass-x and I use the chrome extension. I have very few installed though, so hopefully not a malicious one there.
My account was created in 2013 and changed the password last in 2016. I went back and looked in the audit log for the last year and there was nothing else suspect. Just some failed logins, but that's pretty common, I didn't see any logged in usage from any IPs but mine
installed extensions: ublock origin, OneTab, Lastpass, metamask, cisco webex, edit this cookie