In future versions of Firefox, the browser will display recommended browser extensions that are related to the site that a user is visiting. These extensions will provide extra functionality to a site such as enhancing search functions, protecting a user’s privacy, or performing some other behavior. This new feature is called Contextual Feature Recommender, or CFR, and will recommend extensions that Mozilla feels would be beneficial to users of various sites. Currently this feature is only available in the Firefox Nightly builds, but is expected to be rolled out in Firefox 63.
Source: https://www.bleepingcomputer.com/news/software/firefox-to-recommend-extensions-related-to-sites-you-visit/