Longer story short, the extension creator sold to an ad company that is earning money on the extension in this malicious way.
This is very interesting to me. I use a few extensions, but most are security related. Otherwise I am not a heavy extension user, although I think this means there is some functionality that I am missing from my web browsing experience. Extensions I am used to are basically set and forget. Apparently the extension referenced in this article is useful for Website developers. Sort of a slick, yet shady way to get some income.
Please visit Brian Krebs website and read the article in full: