diff --git a/wp-includes/class-wp-customize-widgets.php b/wp-includes/class-wp-customize-widgets.php
index 40590f0818..a605b90c49 100644
--- a/wp-includes/class-wp-customize-widgets.php
+++ b/wp-includes/class-wp-customize-widgets.php
@@ -35,9 +35,23 @@ final class WP_Customize_Widgets {
 	 * @var array
 	 */
 	protected $core_widget_id_bases = array(
-		'archives', 'calendar', 'categories', 'links', 'meta',
-		'nav_menu', 'pages', 'recent-comments', 'recent-posts',
-		'rss', 'search', 'tag_cloud', 'text',
+		'archives',
+		'calendar',
+		'categories',
+		'custom_html',
+		'links',
+		'media_audio',
+		'media_image',
+		'media_video',
+		'meta',
+		'nav_menu',
+		'pages',
+		'recent-comments',
+		'recent-posts',
+		'rss',
+		'search',
+		'tag_cloud',
+		'text',
 	);
 
 	/**
diff --git a/wp-includes/default-filters.php b/wp-includes/default-filters.php
index 8f0237028d..ada9c53c3f 100644
--- a/wp-includes/default-filters.php
+++ b/wp-includes/default-filters.php
@@ -170,6 +170,8 @@ add_filter( 'widget_text_content', 'wptexturize'          );
 add_filter( 'widget_text_content', 'convert_smilies',  20 );
 add_filter( 'widget_text_content', 'wpautop'              );
 
+add_filter( 'widget_custom_html_content', 'balanceTags' );
+
 add_filter( 'date_i18n', 'wp_maybe_decline_date' );
 
 // RSS filters
diff --git a/wp-includes/default-widgets.php b/wp-includes/default-widgets.php
index 87ad9dbfb3..2585978907 100644
--- a/wp-includes/default-widgets.php
+++ b/wp-includes/default-widgets.php
@@ -60,3 +60,141 @@ require_once( ABSPATH . WPINC . '/widgets/class-wp-widget-tag-cloud.php' );
 
 /** WP_Nav_Menu_Widget class */
 require_once( ABSPATH . WPINC . '/widgets/class-wp-nav-menu-widget.php' );
+
+/**
+ * Core class used to implement a Custom HTML widget.
+ *
+ * Note that this class is only located in this file in the 4.8 branch
+ * for the sake of automatic updates. In 4.9 and above, it is located at
+ * `wp-includes/widgets/class-wp-widget-custom-html.php`.
+ *
+ * @since 4.8.1
+ *
+ * @see WP_Widget
+ */
+class WP_Widget_Custom_HTML extends WP_Widget {
+
+	/**
+	 * Default instance.
+	 *
+	 * @since 4.8.1
+	 * @var array
+	 */
+	protected $default_instance = array(
+		'title' => '',
+		'content' => '',
+	);
+
+	/**
+	 * Sets up a new Custom HTML widget instance.
+	 *
+	 * @since 4.8.1
+	 */
+	public function __construct() {
+		$widget_ops = array(
+			'classname' => 'widget_custom_html',
+			'description' => __( 'Arbitrary HTML code.' ),
+			'customize_selective_refresh' => true,
+		);
+		$control_ops = array(
+			'width' => 400,
+			'height' => 350,
+		);
+		parent::__construct( 'custom_html', __( 'Custom HTML' ), $widget_ops, $control_ops );
+	}
+
+	/**
+	 * Outputs the content for the current Custom HTML widget instance.
+	 *
+	 * @since 4.8.1
+	 *
+	 * @param array $args     Display arguments including 'before_title', 'after_title',
+	 *                        'before_widget', and 'after_widget'.
+	 * @param array $instance Settings for the current Custom HTML widget instance.
+	 */
+	public function widget( $args, $instance ) {
+
+		$instance = array_merge( $this->default_instance, $instance );
+
+		/** This filter is documented in wp-includes/widgets/class-wp-widget-pages.php */
+		$title = apply_filters( 'widget_title', $instance['title'], $instance, $this->id_base );
+
+		$content = $instance['content'];
+
+		/**
+		 * Filters the content of the Custom HTML widget.
+		 *
+		 * @since 4.8.1
+		 *
+		 * @param string                $content  The widget content.
+		 * @param array                 $instance Array of settings for the current widget.
+		 * @param WP_Widget_Custom_HTML $this     Current Custom HTML widget instance.
+		 */
+		$content = apply_filters( 'widget_custom_html_content', $content, $instance, $this );
+
+		echo $args['before_widget'];
+		if ( ! empty( $title ) ) {
+			echo $args['before_title'] . $title . $args['after_title'];
+		}
+		echo $content;
+		echo $args['after_widget'];
+	}
+
+	/**
+	 * Handles updating settings for the current Custom HTML widget instance.
+	 *
+	 * @since 4.8.1
+	 *
+	 * @param array $new_instance New settings for this instance as input by the user via
+	 *                            WP_Widget::form().
+	 * @param array $old_instance Old settings for this instance.
+	 * @return array Settings to save or bool false to cancel saving.
+	 */
+	public function update( $new_instance, $old_instance ) {
+		$instance = array_merge( $this->default_instance, $old_instance );
+		$instance['title'] = sanitize_text_field( $new_instance['title'] );
+		if ( current_user_can( 'unfiltered_html' ) ) {
+			$instance['content'] = $new_instance['content'];
+		} else {
+			$instance['content'] = wp_kses_post( $new_instance['content'] );
+		}
+		return $instance;
+	}
+
+	/**
+	 * Outputs the Custom HTML widget settings form.
+	 *
+	 * @since 4.8.1
+	 *
+	 * @param array $instance Current instance.
+	 * @returns void
+	 */
+	public function form( $instance ) {
+		$instance = wp_parse_args( (array) $instance, $this->default_instance );
+		?>
+		<p>
+			<label for="<?php echo $this->get_field_id( 'title' ); ?>"><?php _e( 'Title:' ); ?></label>
+			<input class="widefat" id="<?php echo $this->get_field_id( 'title' ); ?>" name="<?php echo $this->get_field_name( 'title' ); ?>" type="text" value="<?php echo esc_attr( $instance['title'] ); ?>"/>
+		</p>
+
+		<p>
+			<label for="<?php echo $this->get_field_id( 'content' ); ?>"><?php _e( 'Content:' ); ?></label>
+			<textarea class="widefat code" rows="16" cols="20" id="<?php echo $this->get_field_id( 'content' ); ?>" name="<?php echo $this->get_field_name( 'content' ); ?>"><?php echo esc_textarea( $instance['content'] ); ?></textarea>
+		</p>
+
+		<?php if ( ! current_user_can( 'unfiltered_html' ) ) : ?>
+			<?php
+			$probably_unsafe_html = array( 'script', 'iframe', 'form', 'input', 'style' );
+			$allowed_html = wp_kses_allowed_html( 'post' );
+			$disallowed_html = array_diff( $probably_unsafe_html, array_keys( $allowed_html ) );
+			?>
+			<?php if ( ! empty( $disallowed_html ) ) : ?>
+				<p>
+					<?php _e( 'Some HTML tags are not permitted, including:' ); ?>
+					<code><?php echo join( '</code>, <code>', $disallowed_html ); ?></code>
+				</p>
+			<?php endif; ?>
+		<?php endif; ?>
+		<?php
+	}
+}
diff --git a/wp-includes/widgets.php b/wp-includes/widgets.php
index caa575b149..fbbdcf5f55 100644
--- a/wp-includes/widgets.php
+++ b/wp-includes/widgets.php
@@ -1474,6 +1474,8 @@ function wp_widgets_init() {
 
 	register_widget( 'WP_Nav_Menu_Widget' );
 
+	register_widget( 'WP_Widget_Custom_HTML' );
+
 	/**
 	 * Fires after all default WordPress widgets have been registered.
 	 *
diff --git a/wp-includes/widgets/class-wp-widget-text.php b/wp-includes/widgets/class-wp-widget-text.php
index 6ce1e2f8d0..7d149c0a0f 100644
--- a/wp-includes/widgets/class-wp-widget-text.php
+++ b/wp-includes/widgets/class-wp-widget-text.php
@@ -25,7 +25,7 @@ class WP_Widget_Text extends WP_Widget {
 	public function __construct() {
 		$widget_ops = array(
 			'classname' => 'widget_text',
-			'description' => __( 'Arbitrary text or HTML.' ),
+			'description' => __( 'Arbitrary text.' ),
 			'customize_selective_refresh' => true,
 		);
 		$control_ops = array(