High-profile YouTubers have been impersonated by scammers sending fake messages to subscribers crafted to look like they were sent by the video stars.
The scam messages sent via YouTube's message system asked recipients to click a link to receive a prize.
The names, icons and imagery used by the YouTubers were prominent in the messages to make them look authentic.
YouTube said it was looking into ways to spot and stop the impersonation scams.
Many subscribers to popular YouTubers including Philip DeFranco, James Charles, Jeffree Star, Lewis Hilsenteger from Unbox Therapy, Bhad Bhabie and many others are believed to have received the messages.
Between them the YouTubers have more than 50 million subscribers.
The text in every message is the same, and suggests that a subscriber was picked at random to get a gift.
Philip DeFranco mentioned the scam at the start of one video warning people not to click the link.
He said most people would recognise that it was an "obvious scam" and added that neither he nor other creators it claimed to come from had sent the messages.
YouTube responded via tweet thanking Mr DeFranco for alerting it to the spam problem.
It added: "We're in the process of implementing additional measures to prevent impersonation like this."
It also said that anyone who got the spam YouTube message could block accounts sending them similar messages.