Sorry, if it came across as me implying you pulled that from thin air.
One of the most interesting things we had was the core dumps. Randomnly (depending on memory state) we'd crash rather than dump out memory in the HTTP response. We had all that data going back over the entire period. That gave us a lot of confidence this hadn't been exploited because we could see the rate of crashes plus we could see the actual core dumps to see the memory state when the crash happened.
One of the most interesting things we had was the core dumps. Randomnly (depending on memory state) we'd crash rather than dump out memory in the HTTP response. We had all that data going back over the entire period. That gave us a lot of confidence this hadn't been exploited because we could see the rate of crashes plus we could see the actual core dumps to see the memory state when the crash happened.