They're always permitted to ask, but there's nothing they can do to stop you. Maybe it's a bit rude, but their choice not to reward foreigners under their bug

They're always permitted to ask, but there's nothing they can do to stop you. Maybe it's a bit rude, but their choice not to reward foreigners under their bug bounty is also kind of rude. Neither party has much of a high ground, in my opinion. The blog post was published half a year after KakaoTalk said they fixed the problem, that's twice as long as most people would give them.