While there may be some undesirable programs riding with the downloads, if you pay attention and do some research, cnet downloads have some good, safe ad blockers. I have been happy with their AdFender.
Firefox Anti-Tracking Extensions:
DoNotTrackPlus
https://www.abine.com/
Ghostery
https://www.ghostery.com/
Disconnect
https://disconnect.me/
[Some of the above also work with other browsers. Check the websites.]
I use AdBlockPlus and Abine.com’s DoNotTrack