Index: wp-content/themes/twentyten/category.php
===================================================================
--- wp-content/themes/twentyten/category.php	(revision 54300)
+++ wp-content/themes/twentyten/category.php	(working copy)
@@ -21,7 +21,7 @@
 				<?php
 					$category_description = category_description();
 				if ( ! empty( $category_description ) ) {
-					echo '<div class="archive-meta">' . $category_description . '</div>';
+					echo '<div class="archive-meta">' . esc_html( $category_description ) . '</div>';
 				}
 
 				/*