diff --git a/wp-admin/includes/media.php b/wp-admin/includes/media.php
index 2738a2137b..b9bf72d885 100644
--- a/wp-admin/includes/media.php
+++ b/wp-admin/includes/media.php
@@ -3039,7 +3039,7 @@ function edit_form_image_editor( $post ) {
 														}
 														?>
 	</label>
-	<?php wp_editor( $post->post_content, 'attachment_content', $editor_args ); ?>
+	<?php wp_editor( format_to_edit( $post->post_content ), 'attachment_content', $editor_args ); ?>
 
 	</div>
 	<?php
diff --git a/wp-admin/includes/misc.php b/wp-admin/includes/misc.php
index 333d6eb346..e57b5a5727 100644
--- a/wp-admin/includes/misc.php
+++ b/wp-admin/includes/misc.php
@@ -639,23 +639,46 @@ function set_screen_options() {
 				}
 				break;
 			default:
+				if ( '_page' === substr( $option, -5 ) || 'layout_columns' === $option ) {
+					/**
+					 * Filters a screen option value before it is set.
+					 *
+					 * The filter can also be used to modify non-standard [items]_per_page
+					 * settings. See the parent function for a full list of standard options.
+					 *
+					 * Returning false to the filter will skip saving the current option.
+					 *
+					 * @since 2.8.0
+					 * @since 5.4.2 Only applied to options ending with '_page',
+					 *              or the 'layout_columns' option.
+					 *
+					 * @see set_screen_options()
+					 *
+					 * @param bool   $keep   Whether to save or skip saving the screen option value.
+					 *                       Default false.
+					 * @param string $option The option name.
+					 * @param int    $value  The number of rows to use.
+					 */
+					$value = apply_filters( 'set-screen-option', false, $option, $value ); // phpcs:ignore WordPress.NamingConventions.ValidHookName.UseUnderscores
+				}
+
 				/**
 				 * Filters a screen option value before it is set.
 				 *
-				 * The filter can also be used to modify non-standard [items]_per_page
-				 * settings. See the parent function for a full list of standard options.
+				 * The dynamic portion of the hook, `$option`, refers to the option name.
 				 *
 				 * Returning false to the filter will skip saving the current option.
 				 *
-				 * @since 2.8.0
+				 * @since 5.4.2
 				 *
 				 * @see set_screen_options()
 				 *
-				 * @param bool     $keep   Whether to save or skip saving the screen option value. Default false.
-				 * @param string   $option The option name.
-				 * @param int      $value  The number of rows to use.
+				 * @param bool   $keep   Whether to save or skip saving the screen option value.
+				 *                       Default false.
+				 * @param string $option The option name.
+				 * @param int    $value  The number of rows to use.
 				 */
-				$value = apply_filters( 'set-screen-option', false, $option, $value );
+				$value = apply_filters( "set_screen_option_{$option}", false, $option, $value );
 
 				if ( false === $value ) {
 					return;
diff --git a/wp-admin/themes.php b/wp-admin/themes.php
index 494e952184..40c55a89f4 100644
--- a/wp-admin/themes.php
+++ b/wp-admin/themes.php
@@ -364,7 +364,7 @@ if ( ! is_multisite() && current_user_can( 'edit_themes' ) && $broken_themes = w
 	</tr>
 	<?php foreach ( $broken_themes as $broken_theme ) : ?>
 		<tr>
-			<td><?php echo $broken_theme->get( 'Name' ) ? $broken_theme->display( 'Name' ) : $broken_theme->get_stylesheet(); ?></td>
+			<td><?php echo $broken_theme->get( 'Name' ) ? $broken_theme->display( 'Name' ) : esc_html( $broken_theme->get_stylesheet() ); ?></td>
 			<td><?php echo $broken_theme->errors()->get_error_message(); ?></td>
 			<?php
 			if ( $can_delete ) {
diff --git a/wp-includes/default-filters.php b/wp-includes/default-filters.php
index 6379a55d24..faf14a2490 100644
--- a/wp-includes/default-filters.php
+++ b/wp-includes/default-filters.php
@@ -573,6 +573,7 @@ add_filter( 'the_excerpt_embed', 'wpautop' );
 add_filter( 'the_excerpt_embed', 'shortcode_unautop' );
 add_filter( 'the_excerpt_embed', 'wp_embed_excerpt_attachment' );
 
+add_filter( 'oembed_dataparse', 'wp_filter_oembed_iframe_title_attribute', 5, 3 );
 add_filter( 'oembed_dataparse', 'wp_filter_oembed_result', 10, 3 );
 add_filter( 'oembed_response_data', 'get_oembed_response_data_rich', 10, 4 );
 add_filter( 'pre_oembed_result', 'wp_filter_pre_oembed_result', 10, 3 );
diff --git a/wp-includes/embed.php b/wp-includes/embed.php
index 51ba70de99..2d0f916171 100644
--- a/wp-includes/embed.php
+++ b/wp-includes/embed.php
@@ -780,6 +780,68 @@ function _oembed_create_xml( $data, $node = null ) {
 	return $node->asXML();
 }
 
+/**
+ * Filters the given oEmbed HTML to make sure iframes have a title attribute.
+ *
+ * @since 5.2.0
+ *
+ * @param string $result The oEmbed HTML result.
+ * @param object $data   A data object result from an oEmbed provider.
+ * @param string $url    The URL of the content to be embedded.
+ * @return string The filtered oEmbed result.
+ */
+function wp_filter_oembed_iframe_title_attribute( $result, $data, $url ) {
+	if ( false === $result || ! in_array( $data->type, array( 'rich', 'video' ), true ) ) {
+		return $result;
+	}
+
+	$title = ! empty( $data->title ) ? $data->title : '';
+
+	$pattern = '`<iframe([^>]*)>`i';
+	if ( preg_match( $pattern, $result, $matches ) ) {
+		$attrs = wp_kses_hair( $matches[1], wp_allowed_protocols() );
+
+		foreach ( $attrs as $attr => $item ) {
+			$lower_attr = strtolower( $attr );
+			if ( $lower_attr === $attr ) {
+				continue;
+			}
+			if ( ! isset( $attrs[ $lower_attr ] ) ) {
+				$attrs[ $lower_attr ] = $item;
+				unset( $attrs[ $attr ] );
+			}
+		}
+	}
+
+	if ( ! empty( $attrs['title']['value'] ) ) {
+		$title = $attrs['title']['value'];
+	}
+
+	/**
+	 * Filters the title attribute of the given oEmbed HTML iframe.
+	 *
+	 * @since 5.2.0
+	 *
+	 * @param string $title  The title attribute.
+	 * @param string $result The oEmbed HTML result.
+	 * @param object $data   A data object result from an oEmbed provider.
+	 * @param string $url    The URL of the content to be embedded.
+	 */
+	$title = apply_filters( 'oembed_iframe_title_attribute', $title, $result, $data, $url );
+
+	if ( '' === $title ) {
+		return $result;
+	}
+
+	if ( isset( $attrs['title'] ) ) {
+		unset( $attrs['title'] );
+		$attr_string = join( ' ', wp_list_pluck( $attrs, 'whole' ) );
+		$result      = str_replace( $matches[0], '<iframe ' . trim( $attr_string ) . '>', $result );
+	}
+	return str_ireplace( '<iframe ', sprintf( '<iframe title="%s" ', esc_attr( $title ) ), $result );
+}
+
+
 /**
  * Filters the given oEmbed HTML.
  *
diff --git a/wp-includes/pluggable.php b/wp-includes/pluggable.php
index d4e3fb47d1..9e1357c167 100644
--- a/wp-includes/pluggable.php
+++ b/wp-includes/pluggable.php
@@ -1374,9 +1374,9 @@ if ( ! function_exists( 'wp_validate_redirect' ) ) :
 	 * @return string redirect-sanitized URL
 	 */
 	function wp_validate_redirect( $location, $default = '' ) {
-		$location = trim( $location, " \t\n\r\0\x08\x0B" );
-		// browsers will assume 'http' is your protocol, and will obey a redirect to a URL starting with '//'
-		if ( substr( $location, 0, 2 ) == '//' ) {
+		$location = wp_sanitize_redirect( trim( $location, " \t\n\r\0\x08\x0B" ) );
+		// Browsers will assume 'http' is your protocol, and will obey a redirect to a URL starting with '//'.
+		if ( '//' === substr( $location, 0, 2 ) ) {
 			$location = 'http:' . $location;
 		}