You shouldn't willy-nilly install add-ons, but these are pretty harmless. They don't do anything over the network. These don't change web pages either. They simply interact with the cookie storage. Add-ons that can make you fingerprintable are stuff like NoScript, if you have a unique set of whitelisted domains, or ad blockers, or anything else that changes the page or queriable system properties (like installed fonts).