Question about search string..

I noticed recently that search strings are now different for one of my sites. Why I am getting search strings that automatically include an “x” and “y” parameter for each search query, for example:

/index.php?s=test&x=46&y=12

The x and y values are generally different for each search term(s), often they are zero. I am sure the behavior is due to a plugin, although I can’t seem to remember which one. Any clues would be most appreciated – Thanks!