Ticket #37697: 37697.diff

src/wp-includes/revision.php

@@ -594 +594 @@
                 return $value;
         }
 
-        if ( empty( $_REQUEST['_thumbnail_id'] ) || $post->ID != $post_id || '_thumbnail_id' != $meta_key || 'revision' == $post->post_type ) {
+        if ( empty( $_REQUEST['_thumbnail_id'] ) || $post->ID != $post_id || '_thumbnail_id' != $meta_key || 'revision' == $post->post_type || $post_id != $_REQUEST['preview_id'] ) {
                 return $value;
         }
 

tests/phpunit/tests/post/thumbnails.php

@@ -242 +242 @@
 
                 $GLOBALS['post'] = self::$post;
                 $_REQUEST['_thumbnail_id'] = self::$attachment_id;
+                $_REQUEST['preview_id'] = self::$post->ID;
 
                 $result = _wp_preview_post_thumbnail_filter( '', self::$post->ID, '_thumbnail_id' );
                 $this->assertEquals( self::$attachment_id, $result );