<label for="firstName">Name:</label>
<input
  id="firstName"
  type="text"
  value="<script>alert('XSS Input Success')</script><span>Loading XSS</span>"
  style="margin-top: 1rem;"
/>
<br />
<button
  class="btn btn-primary input-test"
  data-loading-text="<span>Loading XSS</span>"
  type="button"
  style="margin-top: 1rem;"
>
  Click Me
</button>
body {
  padding: 1rem;
}
input {
  width: 500px;
  display: inline-block;
  margin-top: .25rem;
}
button .input-test {
  display: block;
  margin-top: 5rem;
}
$(function () {
  $('.input-test').click(function () {
    var inputValue = $('#firstName').val();
    $(this).data('loadingText', inputValue);
    $(this).button('loading', inputValue);
  });
});

External CSS

  1. https://cdn.jsdelivr.net/npm/bootstrap@3.4.1/dist/css/bootstrap.min.css

External JavaScript

  1. https://cdn.staticfile.net/jquery/2.1.1/jquery.min.js
  2. https://cdn.jsdelivr.net/npm/bootstrap@3.4.1/dist/js/bootstrap.min.js