HI, 

For some reason Paypal has stopped showing the custom field that we populate from our end. We collection donations using a gravity form + PayPal Standard Add-On form. In that gravity-form populates a custom field which is then sent back in the PayPal IPN and is used to cross check for potential spoofing. But since last the 20 days the custom field is not showing up in Paypal donation records and it shows up as empty in PayPal IPNs. As a result our backend gravity-form based donation confirmation is failing. Right now the PayPal IPN looks like this for example:

mc_gross=1.00&protection_eligibility=Ineligible&payer_id=ZNRUYB753B8QG&payment_date=14:34:15 Apr 30, 2019 PDT&payment_status=Completed&charset=windows-1252&first_name=Sudipta&mc_fee=0.32&notify_version=3.9&custom=&payer_status=verified&business=&quantity=1&verify_sign=ApW0719V.01-J90oQDmgwc8nssTuACuJnlofDO9xezXRp-OmIFugkEf4&payer_email=<removed>&txn_id=9L557465MY417450F&payment_type=instant&last_name=<removed>&receiver_email=<removed> &payment_fee=0.32&shipping_discount=0.00&receiver_id=FGBPPUGPKMMSU&insurance_amount=0.00&txn_type=web_accept&item_name=&discount=0.00&mc_currency=USD&item_number=&residence_country=US&shipping_method=Default&transaction_subject=985|d37fa480b5397f4d4ca12777b5a6762e&payment_gross=1.00&ipn_track_id=2626e99b22e75

I also tried changing the Paypal Button Language encoding to UTF-8 but its not helping. The relevant piece of code that supplies custom_field to Paypal is as follows:

$url .= "?notify_url={$ipn_url}&charset=UTF-8&currency_code={$currency}&business={$business_email}&custom={$custom_field}{$invoice}{$customer_fields}{$image_url}{$cancel_url}{$disable_note}{$disable_shipping}{$return_url}"