https://www.bleepingcomputer.com/news/security/chrome-extensions-with-6-million-installs-have-hidden-tracking-code/

A set of 57 Chrome extensions with 6,000,000 users have been discovered with very risky capabilities, such as monitoring browsing behavior, accessing cookies for domains, and potentially executing remote scripts.

These extensions are 'hidden,' meaning they don't show up on Chrome Web Store searches, nor do search engines index them, and can only be installed if the user has the direct URL.