flask-security/flask_security/templates/register.html

<form action="{{ url_for('flask_security.register') }}" method="POST" name="register_form">
  {{ form.hidden_tag() }}
  {{ form.email.label }} {{ form.email }}<br/>
  {{ form.password.label }} {{ form.password }}<br/>
  {{ form.password_confirm.label }} {{ form.password_confirm }}<br/>
  {{ form.submit }}
</form>