Ticket #33645: 33645-4.3.1.patch

src/wp-includes/formatting.php

@@ -596 +596 @@
                 $pee = str_replace(array_keys($pre_tags), array_values($pre_tags), $pee);
 
         // Restore newlines in all elements.
-        $pee = str_replace( " <!-- wpnl --> ", "\n", $pee );
+        if ( false !== strpos( $pee, '<!-- wpnl -->' ) ) {
+                $pee = str_replace( array( ' <!-- wpnl --> ', '<!-- wpnl -->' ), "\n", $pee );
+        }
 
         return $pee;
 }