Well It can be seen here.
3.6 Secure return_url parameter
This function allows the Merchant to be certain that the customer has arrived at the
return_url by completing the payment process – NOT by simply looking up the return_url
value in the page source and entering it in their browser. However, this function ONLY
guarantees that the customer has completed the payment process and NOT that the payment
had been processed.
In order to use this function the Merchant must request this functionality via email to
. Once approved for this function, the Merchant must
ensure that the following are submitted for each transaction:
(i) return_url parameter
(ii) transaction_id parameter
(iii) secret word
(this will be automatically submitted IF entered in your ’Merchant Tools’).
Once the functionality has been activated by our Merchant Service Team and the above
requirements are submitted, we add the following parameters to the return_url:
Rest is here: