Pretty cool, but yeah, you have to be careful of CSS injection (as mentioned by the author). There isn't too much harm that can be done if the user is typing this in himself or herself, but if the search query is pulled from the URL there might be some security implications.

For example, enter this into the search field:

    "]), body, a:not([data-index="

This will hide the entire page. The last "a:not" selector is really inconsequential-- I just had to close the opening parenthesis and this just happens to work.