Technology sometimes runs amok and may result in questionable activities. As an example, not long ago, a Target ad popped up on the Walmart.com Web site — via a practice known as “injected advertising.” This occurred without the knowledge or permission of Walmart.com. This is clearly a practice that is upsetting to many retailers.

How does this happen? Alex Kantrowitz, writing for Ad Age, explains it thusly:

“In one of the most bizarre scenes you’ll see on the Internet, a Target ad recently ran smack in the middle of Walmart.com. The ad wasn’t sold by Wal-Mart, though. That’s because Walmart.com doesn’t even sell the ad space Target bought. But there it was, running in plain sight when Ad Age visited the retail giant’s Web site late last month.”

“This ad was no momentary glitch. It sits at the heart of a scheme that uses browser extensions to place ads on the Web sites of some of the biggest advertisers in the world, including Wal-Mart, Home Depot, Macy’s, Dell, and Samsung. These are forcefully ‘injected’ onto sites and sold by third parties without the owners’ permission. Those third parties pocket the proceeds.

Click the image for an Ad Age video on injected advertising. Then, go full screen for the best viewing.