Index: wp-includes/default-widgets.php
===================================================================
--- wp-includes/default-widgets.php	(revision 12317)
+++ wp-includes/default-widgets.php	(working copy)
@@ -803,8 +803,9 @@
 		if ( empty($title) )
 			$title = __('Untitled');
 
-		$desc = str_replace(array("\n", "\r"), ' ', esc_attr(strip_tags(@html_entity_decode($item->get_description(), ENT_QUOTES, get_option('blog_charset')))));
-		$desc = wp_html_excerpt( $desc, 360 ) . ' […]';
+		$raw_desc = str_replace(array("\n", "\r"), ' ', esc_attr(strip_tags(@html_entity_decode($item->get_description(), ENT_QUOTES, get_option('blog_charset')))));
+		$desc = wp_html_excerpt( $raw_desc, 360 );
+		$desc .= ( mb_strlen( $raw_desc ) > 360 ) ? ' […]' : '';
 		$desc = esc_html( $desc );
 
 		if ( $show_summary ) {