Vulcan/packages/vulcan-payments/lib/stylesheets/style.scss

.stripe-checkout{
  position: relative;
  display: inline-block;
  .spinner{
    position: absolute;
    top: 50%;
    left: 50%;
    margin-left: -20px;
    margin-top: -5px;
    display: none;
  }
  &.checkout-loading{
    div:first-child{
      opacity: 0.2;
      pointer-events: none;
    }
    .spinner{
      display: block;
    }
  }
}