I'm unsure when this started happening, but search result keywords are highlighted on all website pages and posts, after returning from the search results page.
This is reproducible on a fresh WP 3.9 installation with Twenty Fourteen theme and no other plugins. At the Home page search for 'example' to see the search results page where 'example' is properly highlighted. Go to the Home default example page and all 'example' works are highlighted.
Is this expected behaviour?