I launched Firefox (after shutting down the MacBook yesterday) and found that when Firefox restored my previous session as logged in to the WordPress.com Dashboard, I had several new items on my toolbar (or menu bar if you like). New menus had appeared, and familiar menus had new items. If I open a new (tabbed) window in the wordpress.com domain, the menu bar is as usual.
Here are the menus:
[edit - Mark]
Most unusual. No one else has had access to my laptop. Love to know how this happened.