[couchand]

You describe a very real problem, but from what I can tell it's an entirely disjoint context. I'm honestly not clear what the scenario you're suggesting is. Your platform would send an authenticated URL to a verified user over a verified communications channel. There may be applications where the channel of choice is a social media service, but I'm having a hard time seeing why you support that but not support the bog standard OAuth flow for that provider?

Or are you just saying, sometimes a user will receive their authenticated URL on the verified channel and then self-leak it on another channel? In which case, it really doesn't matter what that other channel is...