This feature will be rolling out globally over the coming weeks, starting in the US and Canada.
Blog post in TikTok Newsroom explains: "First, a viewer will see a banner on a video if the content has been reviewed but cannot be conclusively validated. The video's creator will also be notified that their video was flagged as unsubstantiated content. If a viewer attempts to share the flagged video, they’ll see a prompt reminding them that the video has been flagged as unverified content".
TikTok users will see a banner like this one:
This new feature is supposed to stop spreading misinformation.