The amount of data being sent goes beyond what's necessary for the extension to function, especially if you compare to competing solutions such as Google Safe Browsing in Chrome. In the process, it will collect data that allows containing your entire web browsing history and much of your browsing behavior. When you enabled Avast Online Security extension in Firefox, it will request information about your visited websites from an Avast server. So how does these AVG / Avast extensions misused your browser data? Here's a short explanation on this matter. So for existing users these extensions will still be active and continue spying on the users. Mozilla didn’t blacklist the extensions however, stating that they are still talking to Avast. Mozilla immediately disabled the extension listings, so that these extensions can no longer be found on the Mozilla Add-ons site.

So yesterday I reported these four extensions to Mozilla and Google. Avast Secure Browser is a Shareware software in the category Miscellaneous developed by AVAST Software. Avast Browser Cleanup will no longer check for poorly rated toolbars. Untick the option Check my browsers regularly for toolbars with bad user ratings. Spying on your users is clearly a violation of the terms that both Google and Mozilla make extension developers sign. To disable Avast Browser Cleanup from frequently checking for add-ons, go to Avast Browser Cleanup settings: Run Avast Browser Cleanup and click Settings in the left menu.

Disable avast browser cleanup