Issue with tooltip and WCAG validation

This is the fix that I used waiting an update for the plugin:

<script>
(function () {
  'use strict';

  var TIP_ID = 'anww-tip';
  var DEFAULT_TEXT = 'apre una nuova finestra';
  var wired = false;
  var tipObserver = null;

  function isElement(node) {
    return node && node.nodeType === 1 && typeof node.matches === 'function';
  }

  function patchTip(tip) {
    if (!tip) return;
    if (!tip.id) tip.id = TIP_ID;

    var txt = (tip.textContent || '').trim() || DEFAULT_TEXT;
    tip.setAttribute('aria-label', txt);

    var a = document.activeElement;
    if (isElement(a) && a.tagName === 'A' && a.target === '_blank') {
      a.setAttribute('aria-haspopup', 'true');
      a.setAttribute('aria-describedby', TIP_ID);
    }
  }

  function wireTip(tip) {
    if (!tip) return;
    patchTip(tip);

    if (tipObserver) tipObserver.disconnect();
    tipObserver = new MutationObserver(function () {
      requestAnimationFrame(function () { patchTip(tip); });
    });
    tipObserver.observe(tip, { childList: true, characterData: true, subtree: true });
  }

  function hookOnce() {
    if (wired) return;
    var tip = document.querySelector('div.anww-tooltip[role="tooltip"]');
    if (!tip) return;

    wired = true;
    wireTip(tip);

    ['focusin', 'mouseenter'].forEach(function (evt) {
      document.addEventListener(evt, function (e) {
        if (isElement(e.target) && e.target.matches('a[target="_blank"]')) {
          patchTip(tip);
        }
      }, true);
    });

    ['focusout', 'mouseleave'].forEach(function (evt) {
      document.addEventListener(evt, function (e) {
        if (isElement(e.target) && e.target.matches('a[target="_blank"]') &&
          e.target.getAttribute('aria-describedby') === TIP_ID) {
          e.target.removeAttribute('aria-describedby');
        }
      }, true);
    });
  }

  document.addEventListener('DOMContentLoaded', hookOnce);

  var bodyObserver = new MutationObserver(function () {
    var tip = document.querySelector('div.anww-tooltip[role="tooltip"]');
    if (tip) {
      bodyObserver.disconnect();
      hookOnce();
    }
  });
  bodyObserver.observe(document.body, { childList: true, subtree: true });
})();
</script>

Okay, but I suggest you apply a fix like the one I provided earlier to make the plugin ‘false positive’ proof.
In any case, thank you, @alh0319, for the information and the invitation to the meetups, which I will definitely attend in the future, given that website accessibility is becoming increasingly important in my work.