On a iPhone 4/iOS 4 device, sandbox App Store is reporting this error during verification:
21002: The data in the receipt-data property was malformed.
On a iPhone 5/iOS 6 device, the same code works (status == 0, receipt returned) without any problems.
I’ve restarted the device, made sure the Apple ID is logged out, even made a new test user account. Same result. Any ideas?
This Error means the JSON Object that you have created to send for verification is not in correct format.
So My suggestion is to Debug the same on iPhone 4/iOS 4. In case, you are Using Json Framework to create JSON object (for receipt validation) it will work only with iOS 5.0 & above.
Adding Code I had Implemented a few months I Used SBJson to write N parse.