Chrome: overloaded with keyword adds

Problem:  End user was surfing the web in Chrome and noticed an unusual  amount of keyword adds in the copy of the site.  I knew these adds weren’t supposed to be there because I manage one of the webs in question.  Checked “Add/Remove” programs and there weren’t any instances of spyware or malware to uninstall.   Also, checked startup in the registry and msconfig and saw nothing.

Solution:  Realized it might be within Chrome itself.  I went into Chrome’s preferences and looked at the extensions and saw four extensions the end user did not knowingly install.  I deleted them and restarted Chrome. How these extensions got installed, I haven’t a clue.  Has anyone else seen this?