From 7acfab22b8e6f648b89c5c843bf69d920971d570 Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov.ru@gmail.com>
Date: Thu, 28 Nov 2019 00:29:02 +0000
Subject: [PATCH] KSES: Add support for gradient backgrounds.

Props jorgefilipecosta.
Fixes #48376.
Built from https://develop.svn.wordpress.org/trunk@46793


git-svn-id: http://core.svn.wordpress.org/trunk@46593 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/kses.php    | 24 ++++++++++++++++++++++--
 wp-includes/version.php |  2 +-
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/wp-includes/kses.php b/wp-includes/kses.php
index 9c57c3a8e5..846c2dc2be 100644
--- a/wp-includes/kses.php
+++ b/wp-includes/kses.php
@@ -2073,6 +2073,7 @@ function safecss_filter_attr( $css, $deprecated = '' ) {
 	 * @since 5.2.0 Added support for `background-position` and `grid-template-columns`
 	 * @since 5.3.0 Added support for `grid`, `flex` and `column` layout properties.
 	 *              Extend `background-*` support of individual properties.
+	 * @since 5.3.1 Added support for gradient backgrounds.
 	 *
 	 * @param string[] $attr Array of allowed CSS attributes.
 	 */
@@ -2209,6 +2210,15 @@ function safecss_filter_attr( $css, $deprecated = '' ) {
 		'list-style-image',
 	);
 
+	/*
+	 * CSS attributes that accept gradient data types.
+	 *
+	 */
+	$css_gradient_data_types = array(
+		'background',
+		'background-image',
+	);
+
 	if ( empty( $allowed_attr ) ) {
 		return $css;
 	}
@@ -2223,6 +2233,7 @@ function safecss_filter_attr( $css, $deprecated = '' ) {
 		$css_test_string = $css_item;
 		$found           = false;
 		$url_attr        = false;
+		$gradient_attr   = false;
 
 		if ( strpos( $css_item, ':' ) === false ) {
 			$found = true;
@@ -2231,8 +2242,9 @@ function safecss_filter_attr( $css, $deprecated = '' ) {
 			$css_selector = trim( $parts[0] );
 
 			if ( in_array( $css_selector, $allowed_attr, true ) ) {
-				$found    = true;
-				$url_attr = in_array( $css_selector, $css_url_data_types, true );
+				$found         = true;
+				$url_attr      = in_array( $css_selector, $css_url_data_types, true );
+				$gradient_attr = in_array( $css_selector, $css_gradient_data_types, true );
 			}
 		}
 
@@ -2261,6 +2273,14 @@ function safecss_filter_attr( $css, $deprecated = '' ) {
 			}
 		}
 
+		if ( $found && $gradient_attr ) {
+			$css_value = trim( $parts[1] );
+			if ( preg_match( '/^(repeating-)?(linear|radial|conic)-gradient\(([^()]|rgb[a]?\([^()]*\))*\)$/', $css_value ) ) {
+				// Remove the whole `gradient` bit that was matched above from the CSS.
+				$css_test_string = str_replace( $css_value, '', $css_test_string );
+			}
+		}
+
 		// Remove any CSS containing containing \ ( & } = or comments, except for url() useage checked above.
 		if ( $found && ! preg_match( '%[\\\(&=}]|/\*%', $css_test_string ) ) {
 			if ( $css != '' ) {
diff --git a/wp-includes/version.php b/wp-includes/version.php
index cb66e0f818..0f7a300199 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.4-alpha-46792';
+$wp_version = '5.4-alpha-46793';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.