Mozilla has removed four extensions from Avast and AVG from the Firefox addon site over concerns that they were tracking a user’s activity as they are browsed the web. Security researcher Wladimir Palant reported that these extensions are sending a large amount of tracking data. Avast Online Security, Avast SafePrice, and AVG SafePrice extensions have been removed from the Mozilla Firefox addons repository. Palant also reported these extensions on the Google Chrome Web Store, but they are currently still available.
Source: https://www.bleepingcomputer.com/news/software/avast-and-avg-firefox-extensions-pulled-from-mozilla-addons-site/