What is October surprise Hillary Clinton warns Kamala Harris about?

"Russians are active in the election, so is Iran, we know. Chinese uses TikTok; they certainly used against Biden and for Trump. I think they're a little less pro-Trump right now. So you look at where people get there information from and they get their information largely from social media. And so the campaign is doing its best job to combat that both domestic and foreign false disinformation," Hillary said.