I'm sure this is what's happening. Their serializer is perhaps filtering out properties they knew about, but shouldGroupAccessibilityChildren is a new property

I'm sure this is what's happening. Their serializer is perhaps filtering out properties they knew about, but shouldGroupAccessibilityChildren is a new property on the UIAccessibility Protocol which is adopted by NSObject. A good short-term fix is to update the web service, but they should update it to only use the POST parameters it expects. When they release an update to the iOS app, they can fix their serializer to only serialize the properties they need. Apple isn't injecting this - their code is.