Roblox, an online children's game, has 64 million players per month. (Courtesy of Roblox)

Amber Petersen was reading to her daughter a couple of weeks ago when something on the family’s iPad screen caught her eye. Her little girl had been playing Roblox, a popular children’s game that lets players build their own activities and structures with few limits.

What Petersen saw shocked her: While her daughter’s avatar was lying on the ground, two other avatars mimed a violent gang-rape. Petersen snapped screen shots of the scene, thankful at least that she could shield her daughter from the images. Then she posted her story and the images to Facebook to warn other parents that even products aimed at children require constant vigilance.

“After what just took place this morning, I’m actually questioning whether or not I should allow my precious 7-year-old daughter to have access to a screen ever again,” she wrote. “It’s THAT bad.”

As Petersen’s post spread beyond Facebook, appearing on Sky News and in other publications, Roblox scrambled to find out how this could have happened. According to the company’s rules, avatars can’t appear naked, and Roblox certainly doesn’t allow for the kind of behavior Petersen saw. Like so many other online platforms — YouTube, Twitter, Facebook — the company found itself grappling with how to protect its users from others who refuse to play by the rules.

The game is designed to let players of all ages create their own activities. It is known for having an atmosphere where anything goes — an attitude meant to encourage creativity — that has been exploited in the past. With at least 64 million players per month, Roblox has to deal with plenty of bad behavior that has prompted it to change its rules in the past.

Roblox ultimately discovered that someone had hacked a single server of the game, allowing that user to circumvent the rules and upload code that clearly violated the company’s rules. This particular attack was a onetime fault; it just so happened that Petersen’s daughter was in the wrong place at the wrong time.

Tami Bhaumik, Roblox’s vice president of marketing and community safety, said that the company immediately banned the user who injected the bad code and that engineers worked quickly to keep this particular kind of attack from happening again. Roblox has hundreds of moderators who monitor the game’s every moment, she said, and the company is continually working to improve its security.

Roblox provides tools for parents to monitor what their children are doing. There are several options for parents to choose how their children interact with others based on their age and maturity level, including an option to turn off the chat function.

But when asked whether this incident might prompt the company to, for example, make it impossible for the characters to stand closely to or interact with each other, Bhaumik suggested that would go against the spirit of the game. “We focus on making sure that everything is done in a safe and appropriate way. A lot of our players like to jump around together — to jump and dance — and that’s something that’s part of the experience.”

Caroline Knorr, parenting editor at the children’s advocacy group Common Sense Media, said the problems Roblox has with its community are the same as every other online community.

“You find bad apples everywhere,” she said. “That’s a terrible lesson for kids to have to learn, and it’s a reality for interacting with sites like this that have so much open interaction.”

But when parents like Petersen stay close or even play along with their children, Knorr said, it can be an opportunity to teach their children how to deal with bad behavior and report what’s inappropriate.

“I’ve talked to parents who really felt like their kids have learned good communication skills by having to deal with people on Roblox,” Knorr said. “That’s a positive, depending on kid’s age. And it should be guided by parents.”

When reached by The Washington Post, Petersen said that she’ll eventually allow her daughter to play Roblox again — as long as Petersen herself is sitting beside her and the parental controls are in place.