With vulnerability like this - this coin doesn't have any chance.
Fuck it. I had high expectations with this coin.
The question is - are all PoS coins vulnerable to double spending like Navajo?
The More coins one person holds the more control they will have on the network. Sadly!
A big problem.
How can you prevent this from happen again?
Increase the number of confirmations, imho is just a short-term solution.
Maybe even set a ceiling on the stack, so as to limit the power of those who have more, it might help a little.
(Or not a linear function but logarithmic)
Another way of control would need a periodic external confirmation of blockchain, what do you think of an
auto checkpoint system, it might help?