Twitter didn't challenge the legitimacy of the email, but said it doesn't have any comment on private chats with "any advertiser, even a former advertiser."

It's important to note that word of the Democratic National Committee hack had only recently surfaced at the time Twitter was making its offer. And it wasn't alone in unintentionally aiding a Russian propaganda effort. Just this week, word emerged that Facebook gave advertisers electoral demographics that made it easier for Russia to exploit social divisions. The Twitter scoop ultimately illustrates how internet giants weren't fully aware of what could happen by courting key Russian advertisers.