A recent Vice[www.vice.com] report detailed the free antivirus company collecting and selling browser history (including URL, visiting time, order of site visits, search engine query terms, links clicked on Amazon, etc.) to third-party companies.

The data sharing is supposedly opt-in and shows up as during an installation screen for new users and as a prompt for existing users, but the article suggests there are some users have not been made aware of this. So beware.