Children are being subjected to racism, rape threats and sexual material in the metaverse, according to a new BBC report.
That has led a children's charity to blast some apps in the virtual reality (VR) world as "dangerous by design" and a "toxic combination of risks".
A BBC researcher posing as 13-year-old downloaded one app and visited rooms where simulated sex was happening.
Jess Sherwood was also shown sex toys and approached by a number of adult men, the report said.
VRChat, a world where avatars can chat to each other, is marked as being suitable for those over 13-years-old but contains pole-dancing and strip clubs alongside more innocent virtual rooms.
The researcher was also told avatars can "get naked and do unspeakable things", the BBC said.
Head of online child safety policy for the National Society for the Prevention of Cruelty to Children (NSPCC) Andy Burrows said the findings were extraordinary.
"This is a product that is dangerous by design because of oversight and neglect," he said.
"We are seeing products rolled out without any suggestion that safety has been considered. It's children being exposed to entirely inappropriate, really incredibly harmful experiences."
VRChat's website says it has more than 25,000 worlds created by its community, offering an "endless collection of social VR experiences".
"Whether you're looking for new VR experiences or have an idea of your own, VRChat is the place to be."
VRChat is available via multiple platforms, including Steam and Meta's Oculus VR headset, which only requires a Facebook account to download the app.
One safety campaigner who creates YouTube videos told the BBC they remained anonymous because they were concerned for the safety of their family.
They said that during months of investigation into VRChat they had spoken with children who had been forced into virtual sex and were being groomed by adults.
"Predatory and toxic behaviour has no place on the platform," VRChat told the BBC, saying it was "working hard to make itself a safe and welcoming place for everyone".
A VRChat spokesperson told website Engadget that users' safety was its top priority.
"It is likely that, if it were reported, much of the content that you described would be removed immediately," they told the site.
"The users you described were acting in a way that would almost certainly lead to the termination of their accounts had they been reported."
