Grouped backports to the 5.0 branch.

- Media: Prevent CSRF setting attachment thumbnails.
- Embeds: Add protocol validation for WordPress Embed code.
- I18N: Introduce sanitization function for locale.
- Editor: Ensure block comments are of a valid form.

Merges [55760-55764] to the 5.0 branch
Props dd32, isabel_brison, martinkrcho, matveb, ocean90, paulkevan, peterwilsoncc, timothyblynjacobs, xknown, youknowriad.
Built from https://develop.svn.wordpress.org/branches/5.0@55791


git-svn-id: http://core.svn.wordpress.org/branches/5.0@55303 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/about.php

@@ -62,6 +62,26 @@ include( ABSPATH . 'wp-admin/admin-header.php' );
 
 		<div class="changelog point-releases">
 			<h3><?php _e( 'Maintenance and Security Releases' ); ?></h3>
+			<p>
+				<?php
+				printf(
+					/* translators: %s: WordPress version number */
+					__( '<strong>Version %s</strong> addressed some security issues.' ),
+					'5.0.19'
+				);
+				?>
+				<?php
+				printf(
+					/* translators: %s: HelpHub URL */
+					__( 'For more information, see <a href="%s">the release notes</a>.' ),
+					sprintf(
+						/* translators: %s: WordPress version */
+						esc_url( __( 'https://wordpress.org/support/wordpress-version/version-%s/' ) ),
+						sanitize_title( '5.0.19' )
+					)
+				);
+				?>
+			</p>
 			<p>
 				<?php
 				printf(

wp-admin/includes/ajax-actions.php

@@ -2257,6 +2257,10 @@ function wp_ajax_set_attachment_thumbnail() {
 		wp_send_json_error();
 	}
 
+	if ( false === check_ajax_referer( 'set-attachment-thumbnail', '_ajax_nonce', false ) ) {
+		wp_send_json_error();
+	}
+
 	$post_ids = array();
 	// For each URL, try to find its corresponding post ID.
 	foreach ( $_POST['urls'] as $url ) {

wp-includes/blocks.php

@@ -271,6 +271,10 @@ function serialize_blocks( $blocks ) {
 function filter_block_content( $text, $allowed_html = 'post', $allowed_protocols = array() ) {
 	$result = '';
 
+	if ( false !== strpos( $text, '<!--' ) && false !== strpos( $text, '--->' ) ) {
+		$text = preg_replace_callback( '%<!--(.*?)--->%', '_filter_block_content_callback', $text );
+	}
+
 	$blocks = parse_blocks( $text );
 	foreach ( $blocks as $block ) {
 		$block   = filter_block_kses( $block, $allowed_html, $allowed_protocols );
@@ -280,6 +284,19 @@ function filter_block_content( $text, $allowed_html = 'post', $allowed_protocols
 	return $result;
 }
 
+/**
+ * Callback used for regular expression replacement in filter_block_content().
+ *
+ * @private
+ * @since 6.2.1
+ *
+ * @param array $matches Array of preg_replace_callback matches.
+ * @return string Replacement string.
+ */
+function _filter_block_content_callback( $matches ) {
+	return '<!--' . rtrim( $matches[1], '-' ) . '-->';
+}
+
 /**
  * Filters and sanitizes a parsed block to remove non-allowable HTML from block
  * attribute values.

wp-includes/embed.php

@@ -450,7 +450,7 @@ function get_post_embed_html( $width, $height, $post = null ) {
 		 * and edit wp-embed.js directly.
 		 */
 		$output .=<<<JS
-		!function(c,d){"use strict";var e=!1,n=!1;if(d.querySelector)if(c.addEventListener)e=!0;if(c.wp=c.wp||{},!c.wp.receiveEmbedMessage)if(c.wp.receiveEmbedMessage=function(e){var t=e.data;if(t)if(t.secret||t.message||t.value)if(!/[^a-zA-Z0-9]/.test(t.secret)){for(var r,a,i,s=d.querySelectorAll('iframe[data-secret="'+t.secret+'"]'),n=d.querySelectorAll('blockquote[data-secret="'+t.secret+'"]'),o=0;o<n.length;o++)n[o].style.display="none";for(o=0;o<s.length;o++)if(r=s[o],e.source===r.contentWindow){if(r.removeAttribute("style"),"height"===t.message){if(1e3<(i=parseInt(t.value,10)))i=1e3;else if(~~i<200)i=200;r.height=i}if("link"===t.message)if(a=d.createElement("a"),i=d.createElement("a"),a.href=r.getAttribute("src"),i.href=t.value,i.host===a.host)if(d.activeElement===r)c.top.location.href=t.value}}},e)c.addEventListener("message",c.wp.receiveEmbedMessage,!1),d.addEventListener("DOMContentLoaded",t,!1),c.addEventListener("load",t,!1);function t(){if(!n){n=!0;for(var e,t,r=-1!==navigator.appVersion.indexOf("MSIE 10"),a=!!navigator.userAgent.match(/Trident.*rv:11\./),i=d.querySelectorAll("iframe.wp-embedded-content"),s=0;s<i.length;s++){if(!(e=i[s]).getAttribute("data-secret"))t=Math.random().toString(36).substr(2,10),e.src+="#?secret="+t,e.setAttribute("data-secret",t);if(r||a)(t=e.cloneNode(!0)).removeAttribute("security"),e.parentNode.replaceChild(t,e)}}}}(window,document);
+		!function(d,l){"use strict";var e=!1,n=!1;if(l.querySelector)if(d.addEventListener)e=!0;if(d.wp=d.wp||{},!d.wp.receiveEmbedMessage)if(d.wp.receiveEmbedMessage=function(e){var t=e.data;if(t)if(t.secret||t.message||t.value)if(!/[^a-zA-Z0-9]/.test(t.secret)){for(var r,i,a,s=l.querySelectorAll('iframe[data-secret="'+t.secret+'"]'),n=l.querySelectorAll('blockquote[data-secret="'+t.secret+'"]'),o=new RegExp("^https?:$","i"),c=0;c<n.length;c++)n[c].style.display="none";for(c=0;c<s.length;c++)if(r=s[c],e.source===r.contentWindow){if(r.removeAttribute("style"),"height"===t.message){if(1e3<(a=parseInt(t.value,10)))a=1e3;else if(~~a<200)a=200;r.height=a}if("link"===t.message)if(i=l.createElement("a"),a=l.createElement("a"),i.href=r.getAttribute("src"),a.href=t.value,o.test(a.protocol))if(a.host===i.host)if(l.activeElement===r)d.top.location.href=t.value}}},e)d.addEventListener("message",d.wp.receiveEmbedMessage,!1),l.addEventListener("DOMContentLoaded",t,!1),d.addEventListener("load",t,!1);function t(){if(!n){n=!0;for(var e,t,r=-1!==navigator.appVersion.indexOf("MSIE 10"),i=!!navigator.userAgent.match(/Trident.*rv:11\./),a=l.querySelectorAll("iframe.wp-embedded-content"),s=0;s<a.length;s++){if(!(e=a[s]).getAttribute("data-secret"))t=Math.random().toString(36).substr(2,10),e.src+="#?secret="+t,e.setAttribute("data-secret",t);if(r||i)(t=e.cloneNode(!0)).removeAttribute("security"),e.parentNode.replaceChild(t,e)}}}}(window,document);
 JS;
 	}
 	$output .= "\n//--><!]]>";

wp-includes/formatting.php

@@ -2115,6 +2115,29 @@ function sanitize_html_class( $class, $fallback = '' ) {
 	return apply_filters( 'sanitize_html_class', $sanitized, $class, $fallback );
 }
 
+/**
+ * Strips out all characters not allowed in a locale name.
+ *
+ * @since 6.2.1
+ *
+ * @param string $locale_name The locale name to be sanitized.
+ * @return string The sanitized value.
+ */
+function sanitize_locale_name( $locale_name ) {
+	// Limit to A-Z, a-z, 0-9, '_', '-'.
+	$sanitized = preg_replace( '/[^A-Za-z0-9_-]/', '', $locale_name );
+
+	/**
+	 * Filters a sanitized locale name string.
+	 *
+	 * @since 6.2.1
+	 *
+	 * @param string $sanitized   The sanitized locale name.
+	 * @param string $locale_name The locale name before sanitization.
+	 */
+	return apply_filters( 'sanitize_locale_name', $sanitized, $locale_name );
+}
+
 /**
  * Converts lone & characters into `&` (a.k.a. `&`)
  *

wp-includes/js/wp-embed.js

@@ -43,6 +43,7 @@
 
 		var iframes = document.querySelectorAll( 'iframe[data-secret="' + data.secret + '"]' ),
 			blockquotes = document.querySelectorAll( 'blockquote[data-secret="' + data.secret + '"]' ),
+			allowedProtocols = new RegExp( '^https?:$', 'i' ),
 			i, source, height, sourceURL, targetURL;
 
 		for ( i = 0; i < blockquotes.length; i++ ) {
@@ -78,6 +79,11 @@
 				sourceURL.href = source.getAttribute( 'src' );
 				targetURL.href = data.value;
 
+				/* Only follow link if the protocol is in the allow list. */
+				if ( ! allowedProtocols.test( targetURL.protocol ) ) {
+					continue;
+				}
+
 				/* Only continue if link hostname matches iframe's hostname. */
 				if ( targetURL.host === sourceURL.host ) {
 					if ( document.activeElement === source ) {

wp-includes/js/wp-embed.min.js

@@ -1 +1 @@
-!function(c,d){"use strict";var e=!1,n=!1;if(d.querySelector)if(c.addEventListener)e=!0;if(c.wp=c.wp||{},!c.wp.receiveEmbedMessage)if(c.wp.receiveEmbedMessage=function(e){var t=e.data;if(t)if(t.secret||t.message||t.value)if(!/[^a-zA-Z0-9]/.test(t.secret)){for(var r,a,i,s=d.querySelectorAll('iframe[data-secret="'+t.secret+'"]'),n=d.querySelectorAll('blockquote[data-secret="'+t.secret+'"]'),o=0;o<n.length;o++)n[o].style.display="none";for(o=0;o<s.length;o++)if(r=s[o],e.source===r.contentWindow){if(r.removeAttribute("style"),"height"===t.message){if(1e3<(i=parseInt(t.value,10)))i=1e3;else if(~~i<200)i=200;r.height=i}if("link"===t.message)if(a=d.createElement("a"),i=d.createElement("a"),a.href=r.getAttribute("src"),i.href=t.value,i.host===a.host)if(d.activeElement===r)c.top.location.href=t.value}}},e)c.addEventListener("message",c.wp.receiveEmbedMessage,!1),d.addEventListener("DOMContentLoaded",t,!1),c.addEventListener("load",t,!1);function t(){if(!n){n=!0;for(var e,t,r=-1!==navigator.appVersion.indexOf("MSIE 10"),a=!!navigator.userAgent.match(/Trident.*rv:11\./),i=d.querySelectorAll("iframe.wp-embedded-content"),s=0;s<i.length;s++){if(!(e=i[s]).getAttribute("data-secret"))t=Math.random().toString(36).substr(2,10),e.src+="#?secret="+t,e.setAttribute("data-secret",t);if(r||a)(t=e.cloneNode(!0)).removeAttribute("security"),e.parentNode.replaceChild(t,e)}}}}(window,document);
+!function(d,l){"use strict";var e=!1,n=!1;if(l.querySelector)if(d.addEventListener)e=!0;if(d.wp=d.wp||{},!d.wp.receiveEmbedMessage)if(d.wp.receiveEmbedMessage=function(e){var t=e.data;if(t)if(t.secret||t.message||t.value)if(!/[^a-zA-Z0-9]/.test(t.secret)){for(var r,i,a,s=l.querySelectorAll('iframe[data-secret="'+t.secret+'"]'),n=l.querySelectorAll('blockquote[data-secret="'+t.secret+'"]'),o=new RegExp("^https?:$","i"),c=0;c<n.length;c++)n[c].style.display="none";for(c=0;c<s.length;c++)if(r=s[c],e.source===r.contentWindow){if(r.removeAttribute("style"),"height"===t.message){if(1e3<(a=parseInt(t.value,10)))a=1e3;else if(~~a<200)a=200;r.height=a}if("link"===t.message)if(i=l.createElement("a"),a=l.createElement("a"),i.href=r.getAttribute("src"),a.href=t.value,o.test(a.protocol))if(a.host===i.host)if(l.activeElement===r)d.top.location.href=t.value}}},e)d.addEventListener("message",d.wp.receiveEmbedMessage,!1),l.addEventListener("DOMContentLoaded",t,!1),d.addEventListener("load",t,!1);function t(){if(!n){n=!0;for(var e,t,r=-1!==navigator.appVersion.indexOf("MSIE 10"),i=!!navigator.userAgent.match(/Trident.*rv:11\./),a=l.querySelectorAll("iframe.wp-embedded-content"),s=0;s<a.length;s++){if(!(e=a[s]).getAttribute("data-secret"))t=Math.random().toString(36).substr(2,10),e.src+="#?secret="+t,e.setAttribute("data-secret",t);if(r||i)(t=e.cloneNode(!0)).removeAttribute("security"),e.parentNode.replaceChild(t,e)}}}}(window,document);

wp-includes/l10n.php

@@ -139,7 +139,7 @@ function determine_locale() {
 	}
 
 	if ( ! empty( $_GET['wp_lang'] ) && ! empty( $GLOBALS['pagenow'] ) && 'wp-login.php' === $GLOBALS['pagenow'] ) {
-		$determined_locale = sanitize_text_field( $_GET['wp_lang'] );
+		$determined_locale = sanitize_locale_name( wp_unslash( $_GET['wp_lang'] ) );
 	}
 
 	/**

wp-includes/media.php

@@ -3442,7 +3442,8 @@ function wp_enqueue_media( $args = array() ) {
 		/** This filter is documented in wp-admin/includes/media.php */
 		'captions'  => ! apply_filters( 'disable_captions', '' ),
 		'nonce'     => array(
-			'sendToEditor' => wp_create_nonce( 'media-send-to-editor' ),
+			'sendToEditor'           => wp_create_nonce( 'media-send-to-editor' ),
+			'setAttachmentThumbnail' => wp_create_nonce( 'set-attachment-thumbnail' ),
 		),
 		'post'    => array(
 			'id' => 0,

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.0.18';
+$wp_version = '5.0.19';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.