Q:

Malformed response from Paypal IPN instead of VERIFIED or INVALID

Since July 1st we started receiving malformed IPN response from paypal with an odd string at the bottom of the IPN that is neither VERIFIED or INVALID but something like a non binary sign. This happens randomicly and both for payments related IPNs and for preapprovals.
If we try to resend the IPN from the paypal IPN history sometimes they get verified from paypal at the first time, sometime we have to retry more than once. Never happened before and nothing changed on our side in the ipn verification script that is old but work fine with the most part of the IPNs.
We've checked the endpoint and it is correct:
https://www.paypal.com/cgi-bin/webscr
We've tried to resend some of those malformed IPNs and after one or more retry they comes out correctly VERIFIED.
When we try to get those affected IPN validated in the LIVE production, what we get is a bad request because of this odd string at the bottom of the affected IPNs instead of the VERIFIED or INVALID response:
‹      TŽK‚0„ïüŠ•»,M<Œ$¨ÄÔÇb›@‚ûÐøïmáäe’ÙùvgÉ¦¸æ¬mJ8±s
Í=««â-bU²#bÁŠ5Ù')by‰iDzû)é%ÞØÁŽ’Ò2.à&_NKpGŒtJ|ÃæŽþQÞGd¦­r:­>Fj0r²ÀA¯ØžŒôÛçåF“²à&!µ±| é4`¨›ƒ,mþzø3ú  ÿÿ Î[óâ

A:

Finally, just got a "human" answer from Paypal and immediately share it here for those affected by this issue with some workaround:
"Thanks for contacting PayPal Merchant Technical Support. We are so sorry for the late response to you. I acknowledged that you got IPN error HTTP/1.1 400 Bad Request issue. Please kindly note that this is a known issue in PayPal at the moment. Our relevant department is working on it.
...
In addition, you can also do as follows for the workaround to confirm this transaction.

Call GetTransactionDetails API to find this transaction details.
https://developer.paypal.com/docs/classic/api/merchant/GetTransactionDetails_API_Operation_NVP/
Go to your PayPal account to check transaction details.
Download report to find this payment.
Check notification email sent to your email box *** about this payment.

But we'll keep you posted for the update information of this IPN 400 Bad Request problem."
So, it's not a real solution at the moment but just some workaround available for payments (those workarounds, for example, doesn't work for preapprovals where you still have not a payment). 
We even asked why if it is a known issue, there's nothing on it on the paypal-status website where the "notification" product is market as green and in good health. Will update when we have a real solution.

