function doGet(e) {
  const callback = getCallback_(e);

  try {
    if (!callback) {
      throw new Error("Valid callback is required");
    }

    const targetUrl = getTargetUrl_(e);

    if (!isAllowedUrl_(targetUrl)) {
      throw new Error("Only https://siatube.com is allowed");
    }

    const response = UrlFetchApp.fetch(targetUrl, {
      method: "get",
      muteHttpExceptions: true,
      followRedirects: true,
    });

    const statusCode = response.getResponseCode();
    const responseText = response.getContentText();

    if (statusCode < 200 || statusCode >= 300) {
      throw new Error("Request failed with status " + statusCode);
    }

    const data = JSON.parse(responseText);

    return createJsonpOutput_(callback, data);
  } catch (error) {
    const result = {
      ok: false,
      error: getErrorMessage_(error),
    };
    if (callback) {
      return createJsonpOutput_(callback, result);
    }

    return ContentService
      .createTextOutput(JSON.stringify(result))
      .setMimeType(ContentService.MimeType.JSON);
  }
}

function getTargetUrl_(e) {
  const targetUrl =
    e && e.parameter && e.parameter.url
      ? String(e.parameter.url)
      : "";

  if (!targetUrl) {
    throw new Error("url is required");
  }

  return targetUrl;
}

function getCallback_(e) {
  const callback =
    e && e.parameter && e.parameter.callback
      ? String(e.parameter.callback)
      : "";

  if (!callback) {
    return "";
  }

  const callbackPattern =
    /^[A-Za-z_$][0-9A-Za-z_$]*(?:\.[A-Za-z_$][0-9A-Za-z_$]*)*$/;

  return callbackPattern.test(callback)
    ? callback
    : "";
}

function isAllowedUrl_(targetUrl) {
  return (
    targetUrl === "https://siatube.com" ||
    targetUrl.indexOf("https://siatube.com/") === 0
  );
}

function createJsonpOutput_(callback, data) {
  const json = JSON.stringify(data)
    .replace(/\u2028/g, "\\u2028")
    .replace(/\u2029/g, "\\u2029");

  const jsonp = callback + "(" + json + ");";

  return ContentService
    .createTextOutput(jsonp)
    .setMimeType(ContentService.MimeType.JAVASCRIPT);
}

function getErrorMessage_(error) {
  if (error && error.message) {
    return String(error.message);
  }

  return String(error);
}

<script defer data-domain="html.cafe" src="https://milkymouse.com/js/script.js"></script>