Is Great Start - Homepage safe?

// Fires on every search form submission from the new tab page.
// el.preventDefault() stops any direct navigation; the extension
// takes full control and redirects through greatstartapp.com.
document.querySelector('form.search').addEventListener('submit', function (el) {
  const form = new FormData(el.target);
  const provider = form.get('provider');       // e.g. 'yahoo'
  const searchterm = form.get('searchterm');   // the user's query
  el.preventDefault();                         // intercept before any navigation

  let manifestData = chrome.runtime.getManifest();

  // Redirect to greatstartapp.com with all parameters.
  // chrome.runtime.id is persistent for the lifetime of the installation.
  window.location.href =
    'https://greatstartapp.com' +
    '/serp.php?v=' + encodeURIComponent(manifestData.version) +
    '&id='       + encodeURIComponent(chrome.runtime.id) +
    '&q='        + encodeURIComponent(searchterm) +
    '&provider=' + encodeURIComponent(provider);
});