Browser ‘Favicons’ can be used as undeletable ‘Supercookies’ to track you online. Favicons can break through incognito mode, VPNs, and Pi-holes to track your movement online.
Read more of this article here: https://www.vice.com/en/article/n7v5y7/browser-favicons-can-be-used-as-undeletable-supercookies-to-track-you-online