Weird. I disabled the addon after my last post, then went to load the site myself a couple of minutes ago, so about 7 hours later and it loaded up a session for another user that was last online at 10.33am.
Trying to open the alerts menu or user account menu greeted me with a security issue error
Security error occurred. Please press back, refresh the page, and try again.
After a page reload, it found my correct user info and showed my my usual account info.