User-generated content can come from anywhere around the world and at any time. As your site or app grows, you might experience more user-generated content submitted than it's feasible for any single person to review.
Here are some suggested strategies and solutions:
For a variation of this, limit the types of content non-trusted users can submit; e.g., allow text but not images or links.
You can also consider employing human content reviewers or moderators to review the user-generated content on your site or app.