Index: wp-admin/css/customize-controls.css
===================================================================
--- wp-admin/css/customize-controls.css	(revision 38350)
+++ wp-admin/css/customize-controls.css	(working copy)
@@ -1219,7 +1219,8 @@
 }
 
 .add-new-widget:before,
-.add-new-menu-item:before {
+.add-new-menu-item:before,
+#available-menu-items .new-content-item .add-content:before {
 	content: "\f132";
 	display: inline-block;
 	position: relative;
Index: wp-admin/css/customize-nav-menus.css
===================================================================
--- wp-admin/css/customize-nav-menus.css	(revision 38350)
+++ wp-admin/css/customize-nav-menus.css	(working copy)
@@ -61,6 +61,10 @@
 	text-align: right;
 }
 
+.customize-control-nav_menu_item.has-notifications .menu-item-handle {
+	border-left: 4px solid #00a0d2;
+}
+
 .wp-customizer .menu-item-settings {
 	max-width: 100%;
 	overflow: hidden;
@@ -497,7 +501,7 @@
 	color: #23282d;
 }
 
-#available-menu-items .accordion-section-content {
+#available-menu-items .available-menu-items-list {
 	overflow-y: auto;
 	max-height: 200px; /* This gets set in JS to fit the screen size, and based on # of sections. */
 	background: transparent;
@@ -534,11 +538,59 @@
 }
 
 #available-menu-items .accordion-section-content {
-	padding: 1px 15px 15px 15px;
+	max-height: 290px;
 	margin: 0;
-	max-height: 290px;
+	padding: 0;
+	position: relative;
+	background: transparent;
 }
 
+#available-menu-items .accordion-section-content .available-menu-items-list {
+	margin: 0 0 45px 0;
+	padding: 1px 15px 15px 15px;
+}
+
+#available-menu-items .accordion-section-content .available-menu-items-list:only-child { /* Types that do not support new items for the current user */
+	margin-bottom: 0;
+}
+
+#new-custom-menu-item .accordion-section-content {
+	padding: 0 15px 15px 15px;
+}
+
+#available-menu-items .accordion-section-content .new-content-item {
+	width: calc(100% - 30px);
+	padding: 8px 15px;
+	position: absolute;
+	bottom: 0;
+	z-index: 10;
+	background: #eee;
+	display: -webkit-box;
+	display: -moz-box;
+	display: -ms-flexbox;
+	display: -webkit-flex;
+	display: flex;
+}
+
+#available-menu-items .new-content-item .create-item-input {
+	-webkit-box-flex: 10;
+	-webkit-flex-grow: 10;
+	-moz-box-flex: 10;
+	-ms-flex-positive: 10;
+	-ms-flex: 10;
+	flex-grow: 10;
+	margin-left: 5px;
+}
+#available-menu-items .new-content-item .add-content {
+	padding-left: 6px;
+	-webkit-box-flex: 10;
+	-webkit-flex-grow: 10;
+	-moz-box-flex: 10;
+	-ms-flex-positive: 10;
+	-ms-flex: 10;
+	flex-grow: 1;
+}
+
 #available-menu-items .menu-item-tpl {
 	margin: 0;
 }
@@ -546,7 +598,9 @@
 #custom-menu-item-name.invalid,
 #custom-menu-item-url.invalid,
 .menu-name-field.invalid,
-.menu-name-field.invalid:focus {
+.menu-name-field.invalid:focus,
+#available-menu-items .new-content-item .create-item-input.invalid,
+#available-menu-items .new-content-item .create-item-input.invalid:focus {
 	border: 1px solid #f00;
 }
 
Index: wp-admin/js/customize-nav-menus.js
===================================================================
--- wp-admin/js/customize-nav-menus.js	(revision 38350)
+++ wp-admin/js/customize-nav-menus.js	(working copy)
@@ -80,7 +80,48 @@
 	});
 	api.Menus.availableMenuItems = new api.Menus.AvailableItemCollection( api.Menus.data.availableMenuItems );
 
+	api.Menus.insertedAutoDrafts = [];
+
 	/**
+	 * Insert a new `auto-draft` post.
+	 *
+	 * @param {object} params - Parameters for the draft post to create.
+	 * @param {string} params.post_type - Post type to add.
+	 * @param {number} params.title - Post title to use.
+	 * @return {jQuery.promise} Promise resolved with the added post.
+	 */
+	api.Menus.insertAutoDraftPost = function insertAutoDraftPost( params ) {
+		var request, deferred = $.Deferred();
+
+		request = wp.ajax.post( 'customize-nav-menus-insert-auto-draft', {
+			'customize-menus-nonce': api.settings.nonce['customize-menus'],
+			'wp_customize': 'on',
+			'params': params
+		} );
+
+		request.done( function( response ) {
+			if ( response.postId ) {
+				deferred.resolve( response );
+				api.Menus.insertedAutoDrafts.push( response.postId );
+				api( 'nav_menus_created_posts' ).set( _.clone( api.Menus.insertedAutoDrafts ) );
+			}
+		} );
+
+		request.fail( function( response ) {
+			var error = response || '';
+
+			if ( 'undefined' !== typeof response.message ) {
+				error = response.message;
+			}
+
+			console.error( error );
+			deferred.rejectWith( error );
+		} );
+
+		return deferred.promise();
+	};
+
+	/**
 	 * wp.customize.Menus.AvailableMenuItemsPanelView
 	 *
 	 * View class for the available menu items panel.
@@ -100,6 +141,8 @@
 			'click .menu-item-tpl': '_submit',
 			'click #custom-menu-item-submit': '_submitLink',
 			'keypress #custom-menu-item-name': '_submitLink',
+			'click .new-content-item .add-content': '_submitNew',
+			'keypress .create-item-input': '_submitNew',
 			'keydown': 'keyboardAccessible'
 		},
 
@@ -115,6 +158,7 @@
 		pages: {},
 		sectionContent: '',
 		loading: false,
+		addingNew: false,
 
 		initialize: function() {
 			var self = this;
@@ -124,7 +168,7 @@
 			}
 
 			this.$search = $( '#menu-items-search' );
-			this.sectionContent = this.$el.find( '.accordion-section-content' );
+			this.sectionContent = this.$el.find( '.available-menu-items-list' );
 
 			this.debounceSearch = _.debounce( self.search, 500 );
 
@@ -160,7 +204,7 @@
 
 			// Load more items.
 			this.sectionContent.scroll( function() {
-				var totalHeight = self.$el.find( '.accordion-section.open .accordion-section-content' ).prop( 'scrollHeight' ),
+				var totalHeight = self.$el.find( '.accordion-section.open .available-menu-items-list' ).prop( 'scrollHeight' ),
 					visibleHeight = self.$el.find( '.accordion-section.open' ).height();
 
 				if ( ! self.loading && $( this ).scrollTop() > 3 / 4 * totalHeight - visibleHeight ) {
@@ -337,7 +381,7 @@
 				}
 				items = new api.Menus.AvailableItemCollection( items ); // @todo Why is this collection created and then thrown away?
 				self.collection.add( items.models );
-				typeInner = availableMenuItemContainer.find( '.accordion-section-content' );
+				typeInner = availableMenuItemContainer.find( '.available-menu-items-list' );
 				items.each(function( menuItem ) {
 					typeInner.append( itemTemplate( menuItem.attributes ) );
 				});
@@ -356,13 +400,15 @@
 
 		// Adjust the height of each section of items to fit the screen.
 		itemSectionHeight: function() {
-			var sections, totalHeight, accordionHeight, diff;
+			var sections, lists, totalHeight, accordionHeight, diff;
 			totalHeight = window.innerHeight;
 			sections = this.$el.find( '.accordion-section:not( #available-menu-items-search ) .accordion-section-content' );
-			accordionHeight =  46 * ( 2 + sections.length ) - 13; // Magic numbers.
+			lists = this.$el.find( '.accordion-section:not( #available-menu-items-search ) .available-menu-items-list:not(":only-child")' );
+			accordionHeight =  46 * ( 1 + sections.length ) + 14; // Magic numbers.
 			diff = totalHeight - accordionHeight;
 			if ( 120 < diff && 290 > diff ) {
 				sections.css( 'max-height', diff );
+				lists.css( 'max-height', ( diff - 60 ) );
 			}
 		},
 
@@ -456,6 +502,89 @@
 			itemName.val( '' );
 		},
 
+		// Submit handler for keypress (enter) on field and click on button.
+		_submitNew: function( event ) {
+			var container;
+
+			// Only proceed with keypress if it is Enter.
+			if ( 'keypress' === event.type && 13 !== event.which ) {
+				return;
+			}
+
+			if ( this.addingNew ) {
+				return;
+			}
+
+			container = $( event.target ).closest( '.accordion-section' );
+
+			this.submitNew( container );
+		},
+
+		// Creates a new object and adds an associated menu item to the menu.
+		submitNew: function( container ) {
+			var panel = this,
+				itemName = container.find( '.create-item-input' ),
+				title = itemName.val(),
+				dataContainer = container.find( '.available-menu-items-list' ),
+				itemType = dataContainer.data( 'type' ),
+				itemObject = dataContainer.data( 'object' ),
+				itemTypeLabel = dataContainer.data( 'type_label' ),
+				promise;
+
+			if ( ! this.currentMenuControl ) {
+				return;
+			}
+
+			// Only posts are supported currently.
+			if ( 'post_type' !== itemType ) {
+				return;
+			}
+
+			if ( '' === $.trim( itemName.val() ) ) {
+				itemName.addClass( 'invalid' );
+				itemName.focus();
+				return;
+			} else {
+				itemName.removeClass( 'invalid' );
+				container.find( '.accordion-section-title' ).addClass( 'loading' );
+			}
+
+			panel.addingNew = true;
+			itemName.attr( 'disabled', 'disabled' );
+			promise = api.Menus.insertAutoDraftPost( {
+				post_title: title,
+				post_type: itemObject,
+				post_status: 'publish'
+			} );
+			promise.done( function( data ) {
+				var menuItem = {
+					'title': itemName.val(),
+					'type': itemType,
+					'type_label': itemTypeLabel,
+					'object': itemObject,
+					'object_id': data.postId,
+					'url': data.url
+				}, availableItems, $content, itemTemplate;
+
+				// Add new item to menu.
+				panel.currentMenuControl.addItemToMenu( menuItem );
+
+				// Add the new item to the list of available items.
+				menuItem.id = 'post-' + data.postId; // `id` is used for available menu item Backbone models.
+				availableItems = new api.Menus.AvailableItemCollection( [ menuItem ] );
+				api.Menus.availableMenuItemsPanel.collection.add( availableItems.models );
+				$content = container.find( '.available-menu-items-list' ),
+				itemTemplate = wp.template( 'available-menu-item' );
+				$content.prepend( itemTemplate( menuItem ) );
+				$content.scrollTop();
+
+				// Reset the create content form.
+				itemName.val( '' ).removeAttr( 'disabled' );
+				panel.addingNew = false;
+				container.find( '.accordion-section-title' ).removeClass( 'loading' );
+			} );
+		},
+
 		// Opens the panel.
 		open: function( menuControl ) {
 			this.currentMenuControl = menuControl;
@@ -2545,6 +2674,9 @@
 			if ( data.nav_menu_updates || data.nav_menu_item_updates ) {
 				api.Menus.applySavedData( data );
 			}
+
+			// Reset list of inserted auto draft post IDs.
+			api.Menus.insertedAutoDrafts = [];
 		} );
 
 		// Open and focus menu control.
Index: wp-includes/class-wp-customize-manager.php
===================================================================
--- wp-includes/class-wp-customize-manager.php	(revision 38350)
+++ wp-includes/class-wp-customize-manager.php	(working copy)
@@ -1535,7 +1535,7 @@
 		<script type="text/html" id="tmpl-customize-control-notifications">
 			<ul>
 				<# _.each( data.notifications, function( notification ) { #>
-					<li class="notice notice-{{ notification.type || 'info' }} {{ data.altNotice ? 'notice-alt' : '' }}" data-code="{{ notification.code }}" data-type="{{ notification.type }}">{{ notification.message || notification.code }}</li>
+					<li class="notice notice-{{ notification.type || 'info' }} {{ data.altNotice ? 'notice-alt' : '' }}" data-code="{{ notification.code }}" data-type="{{ notification.type }}">{{{ notification.message || notification.code }}}</li>
 				<# } ); #>
 			</ul>
 		</script>
Index: wp-includes/class-wp-customize-nav-menus.php
===================================================================
--- wp-includes/class-wp-customize-nav-menus.php	(revision 38350)
+++ wp-includes/class-wp-customize-nav-menus.php	(working copy)
@@ -56,16 +56,16 @@
 		add_filter( 'customize_refresh_nonces', array( $this, 'filter_nonces' ) );
 		add_action( 'wp_ajax_load-available-menu-items-customizer', array( $this, 'ajax_load_available_items' ) );
 		add_action( 'wp_ajax_search-available-menu-items-customizer', array( $this, 'ajax_search_available_items' ) );
+		add_action( 'wp_ajax_customize-nav-menus-insert-auto-draft', array( $this, 'ajax_insert_auto_draft_post' ) );
 		add_action( 'customize_controls_enqueue_scripts', array( $this, 'enqueue_scripts' ) );
-
-		// Needs to run after core Navigation section is set up.
 		add_action( 'customize_register', array( $this, 'customize_register' ), 11 );
-
 		add_filter( 'customize_dynamic_setting_args', array( $this, 'filter_dynamic_setting_args' ), 10, 2 );
 		add_filter( 'customize_dynamic_setting_class', array( $this, 'filter_dynamic_setting_class' ), 10, 3 );
 		add_action( 'customize_controls_print_footer_scripts', array( $this, 'print_templates' ) );
 		add_action( 'customize_controls_print_footer_scripts', array( $this, 'available_items_template' ) );
 		add_action( 'customize_preview_init', array( $this, 'customize_preview_init' ) );
+		add_action( 'customize_preview_init', array( $this, 'make_auto_draft_status_previewable' ) );
+		add_action( 'customize_save_nav_menus_created_posts', array( $this, 'save_nav_menus_created_posts' ) );
 
 		// Selective Refresh partials.
 		add_filter( 'customize_dynamic_partial_args', array( $this, 'customize_dynamic_partial_args' ), 10, 2 );
@@ -626,6 +626,12 @@
 			'section'  => 'add_menu',
 			'settings' => array(),
 		) ) );
+
+		$this->manager->add_setting( new WP_Customize_Filter_Setting( $this->manager, 'nav_menus_created_posts', array(
+			'transport' => 'postMessage',
+			'default' => array(),
+			'sanitize_callback' => array( $this, 'sanitize_nav_menus_created_posts' ),
+		) ) );
 	}
 
 	/**
@@ -648,6 +654,7 @@
 	 * Return an array of all the available item types.
 	 *
 	 * @since 4.3.0
+	 * @since 4.7.0  Each array item now includes a `$type_label` in in addition to `$title`, `$type`, and `$object`.
 	 * @access public
 	 *
 	 * @return array The available menu item types.
@@ -660,7 +667,8 @@
 			foreach ( $post_types as $slug => $post_type ) {
 				$item_types[] = array(
 					'title'  => $post_type->labels->name,
-					'type'   => 'post_type',
+					'type_label' => $post_type->labels->singular_name,
+					'type' => 'post_type',
 					'object' => $post_type->name,
 				);
 			}
@@ -673,8 +681,9 @@
 					continue;
 				}
 				$item_types[] = array(
-					'title'  => $taxonomy->labels->name,
-					'type'   => 'taxonomy',
+					'title' => $taxonomy->labels->name,
+					'type_label' => $taxonomy->labels->singular_name,
+					'type' => 'taxonomy',
 					'object' => $taxonomy->name,
 				);
 			}
@@ -684,6 +693,7 @@
 		 * Filters the available menu item types.
 		 *
 		 * @since 4.3.0
+		 * @since 4.7.0  Each array item now includes a `$type_label` in in addition to `$title`, `$type`, and `$object`.
 		 *
 		 * @param array $item_types Custom menu item types.
 		 */
@@ -693,6 +703,103 @@
 	}
 
 	/**
+	 * Add a new `auto-draft` post.
+	 *
+	 * @access public
+	 * @since 4.7.0
+	 *
+	 * @param string $post_type The post type.
+	 * @param string $title     The post title.
+	 * @return WP_Post|WP_Error
+	 */
+	public function insert_auto_draft_post( $post_type, $title ) {
+
+		$post_type_obj = get_post_type_object( $post_type );
+		if ( ! $post_type_obj ) {
+			return new WP_Error( 'unknown_post_type', __( 'Unknown post type' ) );
+		}
+
+		add_filter( 'wp_insert_post_empty_content', '__return_false' );
+		$args = array(
+			'post_status' => 'auto-draft',
+			'post_type'   => $post_type,
+			'post_title'  => $title,
+			'post_name'  => sanitize_title( $title ), // Auto-drafts are allowed to have empty post_names, so we need to explicitly set it.
+		);
+		$r = wp_insert_post( wp_slash( $args ), true );
+		remove_filter( 'wp_insert_post_empty_content', '__return_false' );
+
+		if ( is_wp_error( $r ) ) {
+			return $r;
+		} else {
+			return get_post( $r );
+		}
+	}
+
+	/**
+	 * Ajax handler for adding a new auto-draft post.
+	 *
+	 * @access public
+	 * @since 4.7.0
+	 */
+	public function ajax_insert_auto_draft_post() {
+		if ( ! check_ajax_referer( 'customize-menus', 'customize-menus-nonce' ) ) {
+			status_header( 400 );
+			wp_send_json_error( 'bad_nonce' );
+		}
+
+		if ( ! current_user_can( 'customize' ) ) {
+			status_header( 403 );
+			wp_send_json_error( 'customize_not_allowed' );
+		}
+
+		if ( empty( $_POST['params'] ) || ! is_array( $_POST['params'] ) ) {
+			status_header( 400 );
+			wp_send_json_error( 'missing_params' );
+		}
+
+		$params = wp_unslash( $_POST['params'] );
+
+		if ( empty( $params['post_type'] ) ) {
+			status_header( 400 );
+			wp_send_json_error( 'missing_post_type_param' );
+		}
+
+		$post_type_object = get_post_type_object( $params['post_type'] );
+		if ( ! $post_type_object || ! current_user_can( $post_type_object->cap->create_posts ) || ! current_user_can( $post_type_object->cap->publish_posts ) ) {
+			status_header( 403 );
+			wp_send_json_error( 'insufficient_post_permissions' );
+		}
+
+		if ( ! $params['title'] ) {
+			$params['title'] = '';
+		}
+
+		$r = $this->insert_auto_draft_post( $post_type_object->name, $params['post_title'] );
+		if ( is_wp_error( $r ) ) {
+			$error = $r;
+			if ( ! empty( $post_type_object->labels->singular_name ) ) {
+				$singular_name = $post_type_object->labels->singular_name;
+			} else {
+				$singular_name = __( 'Post' );
+			}
+
+			$data = array(
+				/* translators: %1$s is the post type name and %2$s is the error message. */
+				'message' => sprintf( __( '%1$s could not be created: %2$s' ), $singular_name, $error->get_error_message() ),
+			);
+			wp_send_json_error( $data );
+		} else {
+			$post = $r;
+			$data = array(
+				'postId' => $post->ID,
+				'url'    => get_permalink( $post->ID ),
+			);
+			wp_send_json_success( $data );
+		}
+	}
+
+	/**
 	 * Print the JavaScript templates used to render Menu Customizer components.
 	 *
 	 * Templates are imported into the JS use wp.template.
@@ -768,7 +875,7 @@
 					<span class="spinner"></span>
 				</div>
 				<button type="button" class="clear-results"><span class="screen-reader-text"><?php _e( 'Clear Results' ); ?></span></button>
-				<ul class="accordion-section-content" data-type="search"></ul>
+				<ul class="accordion-section-content available-menu-items-list" data-type="search"></ul>
 			</div>
 			<div id="new-custom-menu-item" class="accordion-section">
 				<h4 class="accordion-section-title" role="presentation">
@@ -797,7 +904,20 @@
 				</div>
 			</div>
 			<?php
-			// Containers for per-post-type item browsing; items added with JS.
+			/**
+			 * Filter the content types that do not allow new items to be created from nav menus.
+			 *
+			 * Types are formatted as 'post_type'|'taxonomy' _ post_type_name; for example, 'taxonomy_post_format'.
+			 * Taxonomies are not yet supported by this UI but will be in the future. Post types are only available
+			 * here if `show_in_nav_menus` is true.
+			 *
+			 * @since 4.7.0
+			 *
+			 * @param array  $types  Array of disallowed types.
+			 */
+			$disallowed_new_content_types = apply_filters( 'customize_nav_menus_disallow_new_content_types', array( 'taxonomy_post_format' ) );
+
+			// Containers for per-post-type item browsing; items are added with JS.
 			foreach ( $this->available_item_types() as $available_item_type ) {
 				$id = sprintf( 'available-menu-items-%s-%s', $available_item_type['type'], $available_item_type['object'] );
 				?>
@@ -813,7 +933,20 @@
 							<span class="toggle-indicator" aria-hidden="true"></span>
 						</button>
 					</h4>
-					<ul class="accordion-section-content" data-type="<?php echo esc_attr( $available_item_type['type'] ); ?>" data-object="<?php echo esc_attr( $available_item_type['object'] ); ?>"></ul>
+					<div class="accordion-section-content">
+						<?php if ( 'post_type' === $available_item_type['type'] && ! in_array( $available_item_type['type'] . '_' . $available_item_type['object'], $disallowed_new_content_types, true ) ) : ?>
+							<?php $post_type_obj = get_post_type_object( $available_item_type['object'] ); ?>
+							<?php if ( current_user_can( $post_type_obj->cap->create_posts ) && current_user_can( $post_type_obj->cap->publish_posts ) ) : ?>
+								<div class="new-content-item">
+									<input type="text" class="create-item-input" placeholder="<?php
+									/* translators: %s: Singular title of post type or taxonomy */
+									printf( __( 'Create New %s' ), $post_type_obj->labels->singular_name ); ?>">
+									<button type="button" class="button add-content"><?php _e( 'Add' ); ?></button>
+								</div>
+							<?php endif; ?>
+						<?php endif; ?>
+						<ul class="available-menu-items-list" data-type="<?php echo esc_attr( $available_item_type['type'] ); ?>" data-object="<?php echo esc_attr( $available_item_type['object'] ); ?>" data-type_label="<?php echo esc_attr( isset( $available_item_type['type_label'] ) ? $available_item_type['type_label'] : $available_item_type['type'] ); ?>"></ul>
+					</div>
 				</div>
 				<?php
 			}
@@ -881,6 +1014,70 @@
 	}
 
 	/**
+	 * Make the auto-draft status protected so that it can be queried.
+	 *
+	 * @since 4.7.0
+	 * @access public
+	 */
+	public function make_auto_draft_status_previewable() {
+		global $wp_post_statuses;
+		$wp_post_statuses['auto-draft']->protected = true;
+	}
+
+	/**
+	 * Sanitize post IDs for auto-draft posts created for nav menu items to be published.
+	 *
+	 * @since 4.7.0
+	 * @access public
+	 *
+	 * @param array $value Post IDs.
+	 * @returns array Post IDs.
+	 */
+	public function sanitize_nav_menus_created_posts( $value ) {
+		$post_ids = array();
+		foreach ( wp_parse_id_list( $value ) as $post_id ) {
+			if ( empty( $post_id ) ) {
+				continue;
+			}
+			$post = get_post( $post_id );
+			if ( 'auto-draft' !== $post->post_status ) {
+				continue;
+			}
+			$post_type_obj = get_post_type_object( $post->post_type );
+			if ( ! $post_type_obj ) {
+				continue;
+			}
+			if ( ! current_user_can( $post_type_obj->cap->publish_posts ) ) {
+				continue;
+			}
+			$post_ids[] = $post->ID;
+		}
+		return $post_ids;
+	}
+
+	/**
+	 * Publish the auto-draft posts that were created for nav menu items.
+	 *
+	 * The post IDs will have been sanitized by already by
+	 * `WP_Customize_Nav_Menu_Items::sanitize_nav_menus_created_posts()` to
+	 * remove any post IDs for which the user cannot publish or for which the
+	 * post is not an auto-draft.
+	 *
+	 * @since 4.7.0
+	 * @access public
+	 *
+	 * @param WP_Customize_Setting $setting Customizer setting object.
+	 */
+	public function save_nav_menus_created_posts( $setting ) {
+		$post_ids = $setting->post_value();
+		if ( ! empty( $post_ids ) ) {
+			foreach ( $post_ids as $post_id ) {
+				wp_publish_post( $post_id );
+			}
+		}
+	}
+
+	/**
 	 * Keep track of the arguments that are being passed to wp_nav_menu().
 	 *
 	 * @since 4.3.0
Index: wp-includes/class-wp-customize-setting.php
===================================================================
--- wp-includes/class-wp-customize-setting.php	(revision 38350)
+++ wp-includes/class-wp-customize-setting.php	(working copy)
@@ -498,6 +498,8 @@
 	/**
 	 * Fetch and sanitize the $_POST value for the setting.
 	 *
+	 * During a save request prior to save, post_value() provides the new value while value() does not.
+	 *
 	 * @since 3.4.0
 	 *
 	 * @param mixed $default A default value which is used as a fallback. Default is null.
Index: wp-includes/kses.php
===================================================================
--- wp-includes/kses.php	(revision 38350)
+++ wp-includes/kses.php	(working copy)
@@ -551,7 +551,7 @@
 	$allowed_protocols = wp_allowed_protocols();
 	$string = wp_kses_no_null( $string, array( 'slash_zero' => 'keep' ) );
 	$string = wp_kses_js_entities( $string );
-	
+
 	// Preserve leading and trailing whitespace.
 	$matches = array();
 	preg_match('/^\s*/', $string, $matches);
@@ -563,7 +563,7 @@
 	} else {
 		$string = substr( $string, strlen( $lead ), -strlen( $trail ) );
 	}
-	
+
 	// Parse attribute name and value from input.
 	$split = preg_split( '/\s*=\s*/', $string, 2 );
 	$name = $split[0];
@@ -600,7 +600,7 @@
 		$value = '';
 		$vless = 'y';
 	}
-	
+
 	// Sanitize attribute by name.
 	wp_kses_attr_check( $name, $value, $string, $vless, $element, $allowed_html );
 
@@ -1063,7 +1063,7 @@
 	} else {
 		$xhtml_slash = '';
 	}
-	
+
 	// Split it
 	$attrarr = wp_kses_hair_parse( $attr );
 	if ( false === $attrarr ) {
@@ -1073,7 +1073,7 @@
 	// Make sure all input is returned by adding front and back matter.
 	array_unshift( $attrarr, $begin . $slash . $elname );
 	array_push( $attrarr, $xhtml_slash . $end );
-	
+
 	return $attrarr;
 }
 
@@ -1714,35 +1714,56 @@
 	 * @param array $attr List of allowed CSS attributes.
 	 */
 	$allowed_attr = apply_filters( 'safe_style_css', array(
+		'-moz-box-flex',
+		'-moz-box-ordinal-group',
+		'-ms-flex',
+		'-ms-flex-order',
+		'-webkit-box-flex',
+		'-webkit-box-ordinal-group',
+		'-webkit-flex',
+		'-webkit-order',
+		'align-content',
+		'align-items',
+		'align-self',
 		'background',
 		'background-color',
-
 		'border',
-		'border-width',
-		'border-color',
-		'border-style',
-		'border-right',
-		'border-right-color',
-		'border-right-style',
-		'border-right-width',
 		'border-bottom',
 		'border-bottom-color',
 		'border-bottom-style',
 		'border-bottom-width',
+		'border-collapse',
+		'border-color',
 		'border-left',
 		'border-left-color',
 		'border-left-style',
 		'border-left-width',
+		'border-right',
+		'border-right-color',
+		'border-right-style',
+		'border-right-width',
+		'border-spacing',
+		'border-style',
 		'border-top',
 		'border-top-color',
 		'border-top-style',
 		'border-top-width',
-
-		'border-spacing',
-		'border-collapse',
+		'border-width',
 		'caption-side',
-
+		'clear',
 		'color',
+		'cursor',
+		'direction',
+		'display',
+		'flex',
+		'flex',
+		'flex-basis',
+		'flex-direction',
+		'flex-flow',
+		'flex-grow',
+		'flex-shrink',
+		'flex-wrap',
+		'float',
 		'font',
 		'font-family',
 		'font-size',
@@ -1749,39 +1770,32 @@
 		'font-style',
 		'font-variant',
 		'font-weight',
+		'height',
+		'justify-content',
 		'letter-spacing',
 		'line-height',
-		'text-decoration',
-		'text-indent',
-		'text-align',
-
-		'height',
-		'min-height',
-		'max-height',
-
-		'width',
-		'min-width',
-		'max-width',
-
+		'list-style-type',
 		'margin',
-		'margin-right',
 		'margin-bottom',
 		'margin-left',
+		'margin-right',
 		'margin-top',
-
+		'max-height',
+		'max-width',
+		'min-height',
+		'min-width',
+		'order',
+		'overflow',
 		'padding',
-		'padding-right',
 		'padding-bottom',
 		'padding-left',
+		'padding-right',
 		'padding-top',
-
-		'clear',
-		'cursor',
-		'direction',
-		'float',
-		'overflow',
+		'text-align',
+		'text-decoration',
+		'text-indent',
 		'vertical-align',
-		'list-style-type',
+		'width',
 	) );
 
 	if ( empty($allowed_attr) )