There are widespread reports that the McAfee browser security software is automatically +1'ing search results within Google.
A Google Web Search Help thread has several reports with these complaints. The first complaint read:
I managed to disable +1 buttons using AdBlock Plus, and the +1 buttons no longer show up in my searches. However, underneath every link it still says "You +1'd this publicly. Undo." Clicking the Undo link does nothing, perhaps because I never +1'd anything.
Google believes it is McAfee's fault based on one user saying when he turned off McAfee it went away. The user said:
When I change the setting on MacAfee to "do not show ratings" and refresh the search page, the "You +1'd this publicly. Undo" notices disappear.
So it's MacAfee related at least for me.
So give that a try and someone should notify McAfee of the issue so they can fix it at the software level. Or maybe Google should fix something?
Forum discussion at Google Web Search Help.
Update: McAfee sent us a statement:
McAfee technology does not +1 any results. What you're seeing is an issue with Adblock.
As you know, if you login to your gmail account, then you see the +1. If you log out, you will not see +1. When you use SiteAdvisor and Adblock, Adblock suppresses the +1 image but not the other +1 content. Remove SiteAdvisor, and Adblock removes it all. Adblock doesn’t expect SiteAdvisor’s icon to be present.