diff -u b/core/modules/media/css/oembed.frame.css b/core/modules/media/css/oembed.frame.css
--- b/core/modules/media/css/oembed.frame.css
+++ b/core/modules/media/css/oembed.frame.css
@@ -2,8 +2,6 @@
   position: absolute;
   left: 0;
   top: 0;
-  right: 0;
-  bottom: 0;
   margin: 0;
   width: 100%;
   height: 100%;
diff -u b/core/themes/stable/css/media/oembed.frame.css b/core/themes/stable/css/media/oembed.frame.css
--- b/core/themes/stable/css/media/oembed.frame.css
+++ b/core/themes/stable/css/media/oembed.frame.css
@@ -2,8 +2,6 @@
   position: absolute;
   left: 0;
   top: 0;
-  right: 0;
-  bottom: 0;
   margin: 0;
   width: 100%;
   height: 100%;