Index: wp-includes/category.php
===================================================================
--- wp-includes/category.php	(revision 12129)
+++ wp-includes/category.php	(working copy)
@@ -351,15 +351,17 @@
 		$category->cat_ID = &$category->term_id;
 		$category->category_count = &$category->count;
 		$category->category_description = &$category->description;
-		$category->cat_name = &$category->name;
-		$category->category_nicename = &$category->slug;
+		$category->cat_name = esc_attr(&$category->name);
+		$category->category_nicename = esc_attr(apply_filters('editable_slug',&$category->slug));
+		$category->slug = esc_attr(apply_filters('editable_slug',&$category->slug));
 		$category->category_parent = &$category->parent;
 	} elseif ( is_array( $category ) && isset( $category['term_id'] ) ) {
 		$category['cat_ID'] = &$category['term_id'];
 		$category['category_count'] = &$category['count'];
 		$category['category_description'] = &$category['description'];
-		$category['cat_name'] = &$category['name'];
-		$category['category_nicename'] = &$category['slug'];
+		$category['cat_name'] = esc_attr(apply_filters('editable_slug',&$category['name']));
+		$category['category_nicename'] = esc_attr(apply_filters('editable_slug',&$category['slug']));
+		$category['slug'] = esc_attr(&$category['slug']);
 		$category['category_parent'] = &$category['parent'];
 	}
 }