This is a privacy violation and must be changed immediately.

https://vec.wikipedia.org/wiki/Wikipedia:Prinsipio loads third-party stuff from addthis.com for everyone visiting the website (logged in or not), due to https://vec.wikipedia.org/wiki/MediaWiki:Gadget-addThisMain.js being set as a default-enabled (!) gadget on https://vec.wikipedia.org/wiki/Speçałe:Preferense#mw-prefsection-gadgets

CC'ing @Fierodelveneto per edit history of https://vec.wikipedia.org/wiki/MediaWiki:Gadgets-definition and as the author of that gadget.

Furthermore, for opt-in, https://vec.wikipedia.org/wiki/Speçałe:Preferense#mw-prefsection-gadgets could say that enabling such gadgets will send your personal data to a third-party.

See also https://vec.wikipedia.org/wiki/MediaWiki:Gadget-addThisArticles.js (but that is at least opt-in).