Mozilla officially launched their new Activity Stream Snippets in Firefox 64 on Monday. These new snippets appear at the bottom of the New Tab page and include call to actions for giving donations, newsletter signups, and learning about the Mozilla podcast and Pocket offerings. These snippets are used to promote various offerings by Firefox. Mozilla bug report says these new snippets launched on January 7th for 1% of the total Firefox 64 users and finally increases to a 100% rollout by January 17th 2019. Using the AS Router Admin, it is possible to see a demo of the available activity stream snippets using a special devtool.
Source: https://www.bleepingcomputer.com/news/software/activity-stream-snippets-launched-in-firefox-to-market-mozilla-offerings/