This null edit to an article (https://en.wikipedia.org/w/index.php?title=List_of_Sam_%26_Cat_episodes&diff=562710419&oldid=562703260) made the category hidden inside of a template in use on the page (template in question: http://en.wikipedia.org/wiki/Template:Episode_list) visible in the editor. It should not be visible.
Version: unspecified
Severity: normal