One of the most popular apps these days among young teenagers and pre-teens is Musical.ly, a seemingly harmless and fun app that allows people to record, upload and share short and silly lip-sync videos. It's consistently in the top 20 most downloaded apps for iPhones and several times has been the #1 most downloaded free app.

While it appears, on the surface to parents, as a fun little app for kids to be kids, there are provocative videos many parents would not want their kids to see. Videos of kids who appear to be 9 or 10 years old, sharing sexually explicit videos of themselves lip-syncing to popular songs with lyrics about oral sex and even acting out the videos. Other videos show young girls taking their clothes off and boys imitating having sex.

"It's definitely music and suggestive motions that I would not want my child to see," mom Kathryn Good said.

She had heard of the app from other parents, but her children hadn ot used it.

Heather Svien, the mother of a 12-year-old daughter, was also familiar with Musical.ly after someone began sending her daughter messages. Someone she did not know.

"They had exchanged phone numbers, so they were texting back and forth," she told me. "It was...it was clearly a creeper."

Musical.ly is intended for people over the age of 13 but like most social media apps, there is no verification required, and anyone can lie about their age whether they're 9 or 49.

On the Musical.ly website, the company states personal information gathered when a user signs up can be shared. That information includes their username, profile and photo. Parents can make their child's account private, meaning only their friends can see their videos. But anyone with a Musical.ly account can see videos posted by others that are made publicly.

Also, some of the most sexually charged and provocative videos, which clearly identify the young users by their face and username, are posted to YouTube.

Like Twitter and Instagram, Musical.ly users use hashtags so others can find videos of a certain subject such as videos of young girls belly-dancing "hash-tagged" as 'ultra low pants'.

After the incident with her daughter, Svien immediately deleted the app from her phone but, she said, "you can't delete musical.ly, the account. You can delete it off your phone and delete the videos you have posted. I messaged Musical.ly to have her account deleted but I have not heard back."

According to the most recent statistics Musical.ly claims around 200 million users. For some perspective, Snapchat, the popular app among teenagers 18 and older, has 187 million.