I don't think it is fair to IPInfo to give the specifics publicly, because once you have the "ah ha" moment you realize it is an entire class of difficult to address problems with how they use their sensor network. That knowledge only helps the bad guys.
Why do we assume that only "bad guys" would want to bypass internet censorship?
We are actively trying to improve our system and build it as figuratively 'antifragile'. We can not afford to get comfortable and we need to constantly find faults in it. If you know anything, you can contact our founder or me directly.
The problem is that everyone knows we are the most accurate data provider and our growth is exponential. To my knowledge, most cybersecurity teams use our data to some degree. We cannot risk having any secrets out there that could disrupt the accuracy of the system. We are aware of several cases where accuracy may be affected, with the most notable being adversarial geofeed submissions.
If the issue is an adversarial geofeed submission, it is a well-known problem. When active measurement fails, we have to fallback to some location hint. There are layers of location hints we have to fall through to ultimately landing on echoing geofeed location hint.
But aside from that... I'm not sure what could possibly impact us. A substantial systemic malicious change in data accuracy seems highly unlikely and quite impossible.