<form id="pa-form" method="post" action="{{ acsurl }}">
    <input type="hidden" name="PaReq" value="{{ pareq }}">
    <input type="hidden" name="TermUrl" value="{{ protocol }}://{{ domain }}{% url 'sagepaypi:complete_3d_secure' tidb64 token %}">
    <input type="hidden" name="MD" value="{{ transaction_id }}">
</form>
<script>
    document.addEventListener("DOMContentLoaded", function() {
        var b=document.getElementById("pa-form");
        b&&b.submit();
    })
</script>