diff -r be944660c56a -r 3d72ae0968f4 wp/wp-includes/customize/class-wp-customize-custom-css-setting.php
--- a/wp/wp-includes/customize/class-wp-customize-custom-css-setting.php	Wed Sep 21 18:19:35 2022 +0200
+++ b/wp/wp-includes/customize/class-wp-customize-custom-css-setting.php	Tue Sep 27 16:37:53 2022 +0200
@@ -145,18 +145,22 @@
 	}
 
 	/**
-	 * Validate CSS.
+	 * Validate a received value for being valid CSS.
 	 *
 	 * Checks for imbalanced braces, brackets, and comments.
 	 * Notifications are rendered when the customizer state is saved.
 	 *
 	 * @since 4.7.0
 	 * @since 4.9.0 Checking for balanced characters has been moved client-side via linting in code editor.
+	 * @since 5.9.0 Renamed `$css` to `$value` for PHP 8 named parameter support.
 	 *
-	 * @param string $css The input string.
+	 * @param string $value CSS to validate.
 	 * @return true|WP_Error True if the input was validated, otherwise WP_Error.
 	 */
-	public function validate( $css ) {
+	public function validate( $value ) {
+		// Restores the more descriptive, specific name for use within this method.
+		$css = $value;
+
 		$validity = new WP_Error();
 
 		if ( preg_match( '#</?\w+#', $css ) ) {
@@ -173,11 +177,15 @@
 	 * Store the CSS setting value in the custom_css custom post type for the stylesheet.
 	 *
 	 * @since 4.7.0
+	 * @since 5.9.0 Renamed `$css` to `$value` for PHP 8 named parameter support.
 	 *
-	 * @param string $css The input value.
+	 * @param string $value CSS to update.
 	 * @return int|false The post ID or false if the value could not be saved.
 	 */
-	public function update( $css ) {
+	public function update( $value ) {
+		// Restores the more descriptive, specific name for use within this method.
+		$css = $value;
+
 		if ( empty( $css ) ) {
 			$css = '';
 		}