Came across this issue today when I investigated some beta user reports... We have used on-device receipt verification for several years, and this was the first time I've ever seen a receipt with the correct signature but with bundle_id set to null (and it is not unassigned but actually a string with the contents set to "null")... Anyways, in our case I managed to narrow it down to being receipts that is downloaded from AppStore using the SKReceiptRefreshRequest while the app has been installed from TestFlight... When I install the latest AppStore version and request the receipt with the same API call, I get a correct receipt with bundle_id set to the expected value, and when I install the TestFlight version and request the receipt, I get a signature valid receipt, but with an invalid bundle_id (and lots of other fields are missing as well)