For quite some time, the applications we trust and use every day have been tricking us into installing extra stuff we don’t need during the update process.
One example is Adobe Flash (pictured below). Sometimes, their “gift” to you is the Chrome browser. Other times, it’s the Ask toolbar. In this case, it’s McAfee Security Scanner. Almost always, you don’t need or want it.
You can avoid it by paying attention to the update screen and unchecking the box next to whatever it’s trying to install for you.