Index: src/wp-includes/media.php
===================================================================
--- src/wp-includes/media.php	(revision 53391)
+++ src/wp-includes/media.php	(working copy)
@@ -3156,6 +3156,7 @@
  * WordPress mp4s in a post.
  *
  * @since 3.6.0
+ * @since 6.1.0 Add support for the muted attribute.
  *
  * @global int $content_width
  *
@@ -3168,6 +3169,7 @@
  *     @type string $poster   The 'poster' attribute for the `<video>` element. Default empty.
  *     @type string $loop     The 'loop' attribute for the `<video>` element. Default empty.
  *     @type string $autoplay The 'autoplay' attribute for the `<video>` element. Default empty.
+ *     @type string $muted    The 'muted' attribute for the `<video>` element. Default false.
  *     @type string $preload  The 'preload' attribute for the `<video>` element.
  *                            Default 'metadata'.
  *     @type string $class    The 'class' attribute for the `<video>` element.
@@ -3212,6 +3214,7 @@
 		'poster'   => '',
 		'loop'     => '',
 		'autoplay' => '',
+		'muted'    => 'false',
 		'preload'  => 'metadata',
 		'width'    => 640,
 		'height'   => 360,
@@ -3339,11 +3342,12 @@
 		'poster'   => esc_url( $atts['poster'] ),
 		'loop'     => wp_validate_boolean( $atts['loop'] ),
 		'autoplay' => wp_validate_boolean( $atts['autoplay'] ),
+		'muted'    => wp_validate_boolean( $atts['muted'] ),
 		'preload'  => $atts['preload'],
 	);
 
 	// These ones should just be omitted altogether if they are blank.
-	foreach ( array( 'poster', 'loop', 'autoplay', 'preload' ) as $a ) {
+	foreach ( array( 'poster', 'loop', 'autoplay', 'preload', 'muted' ) as $a ) {
 		if ( empty( $html_atts[ $a ] ) ) {
 			unset( $html_atts[ $a ] );
 		}