View file rusnet-interactive-map/classes/class-api.php

<?php
if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

class Rusnetim_API {

    public static function get_api_url( $locale = null, $apikey = '' ) {
        if ( ! $locale ) {
            $locale = Rusnetim_Options::sanitize_locale( get_locale() );
        }
        $apikey_param = $apikey ? '&apikey=' . rawurlencode( $apikey ) : '';
        return 'https://api-maps.yandex.ru/2.1/?lang=' . rawurlencode( $locale ) . $apikey_param;
    }

    public static function ajax_get_attachment_image() {
        check_ajax_referer( 'rusnetim_ajax_nonce', 'nonce' );

        if ( empty( $_POST['attachment_id'] ) ) {
            wp_send_json_error();
        }

        $id = intval( wp_unslash( $_POST['attachment_id'] ) );
        $image_url = wp_get_attachment_image_url( $id, 'thumbnail' );

        if ( $image_url ) {
            wp_send_json_success( array( 'url' => $image_url ) );
        } else {
            wp_send_json_error();
        }
    }
}

add_action( 'wp_ajax_rusnetim_get_attachment_image', [ 'Rusnetim_API', 'ajax_get_attachment_image' ] );