Speaking of "avast! icon on the browser navigation bar", the settings with regard to social network sites aren't kept. When I want to share something via Sharethis on Twitter/Facebook, avast! has blocked this. I regularly have unblock this.
If you are using Firefox, you have to allow cookies to remain when Firefox is closed for the AOS anti tracking settings to be retained.
You can also disable the AOS add on/extension for the browser if you prefer.
And you can also selectively uninstall both AOS and Safe Zone if you don't want to use them.