*
	 * @since 6.2.0
	 * @since 6.4.0 Changed method visibility to protected.
	 *
	 * @param string $css CSS to validate.
	 * @return true|WP_Error True if the input was validated, otherwise 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;
	}
}
<br />
<b>Fatal error</b>:  require_once(): Failed opening required '/home/ocb/public_html/wp-includes/blocks/term-description.php' (include_path='.:/opt/alt/php74/usr/share/pear') in <b>/home/ocb/public_html/wp-includes/blocks/require-dynamic-blocks.php</b> on line <b>70</b><br />
<br />
<b>Fatal error</b>:  Uncaught Error: Call to a member function set() on null in /home/ocb/public_html/wp-includes/l10n.php:856
Stack trace:
#0 /home/ocb/public_html/wp-includes/l10n.php(959): load_textdomain('default', '/home/ocb/publi...', 'lv')
#1 /home/ocb/public_html/wp-includes/class-wp-fatal-error-handler.php(49): load_default_textdomain()
#2 [internal function]: WP_Fatal_Error_Handler-&gt;handle()
#3 {main}
  thrown in <b>/home/ocb/public_html/wp-includes/l10n.php</b> on line <b>856</b><br />