wp-includes/rest-api/endpoints/class-wp-rest-global-styles-controller.php:670Validate style.css as valid CSS.
$cssstringtrue|WP_Error protected function validate_custom_css( $css ) { if ( preg_match( '#</?\w+#', $css ) ) { return new WP_Error( 'rest_custom_css_illegal_markup', __( 'Markup is not allowed in CSS.' ), array( 'status' => 400 ) ); } return true; }Introduced in 6.2.0. One change between 6.7.7 and 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
$css retyped from string to mixed.verified against sourcesrc/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-controller.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.