How do I delete "Congratulations" Adware?

I have one of those "Congratulations" pop-ups when I visit Huffingtonpost.com on Safari (and Chrome). I tried the following to get rid of it:

Safari > File > Clear History

Safari > Preferences > Extensions (none)

Safari > Preferences > Privacy > Manage Website Data > Remove All

Safari > Preferences > Security > Block pop up windows is checked

Safari > Develop > Clear Cache

I have shut the computer down after these steps. But the pop up keeps popping up. It shows up on Chrome with Huffpost too.

I've attached a screenshot of the pop-up. Today, it's an Amazon card! Yesterday, it was Walmart.

Any suggestions on how to get rid of this?

Any suggestions?