Children can be as little as three clicks away from inappropriate content on YouTube, says an internet safety expert.
Kspersky Lab examined the "suggested videos" appearing alongside the videos of popular children's TV programmes like Peppa Pig and Dora the Explorer.
It found that users were on average just three clicks away from hitting something aimed at a much older audience.
Clicking onto other videos in the "suggested" panel could quickly take children to music videos featuring violence, nudity and swearing, or other content that would be post-watershed if it were for TV.
The simple searches reveal the dangers if parents do not activate parental controls or leave children unattended while browsing.
With children growing up surrounded by technology, Kaspersky Lab says kids are becoming more and more internet savvy.
Mother of two young boys, Angela Woodward comments, "As the parent of a five-year-old boy with a keen interest in Fireman Sam and Power Rangers, this is an issue I'm really concerned about.
"Although I'm careful to monitor Sam's activity when he goes online, in the past he's been able to click through to things that aren't suitable for his age.
"Now that he's at school and his spelling and writing are getting better I'm afraid this problem will only get worse."
David Emm, senior security researcher at Kaspersky Lab, urged parents to take responsibility for the online safety of their children.
"It's worrying to see just how simple it is for children to access videos of an adult nature on YouTube," he said.
"With younger generations becoming more IT literate and parents increasingly turning to mobile devices, online games and apps as a means of entertaining their kids, these results highlight the importance of taking steps to protect them online.
"Having parental controls in place is vital and can be highly effective in combatting objectionable material. YouTube's Safety Mode feature aims to help parents screen out unsuitable content, but it can't provide 100% protection."
David has these tips for protecting your family online:
Supervision - This may seem obvious, but supervise your child's Internet use. Encourage them to visit and stay on websites you're familiar with. If you have any concerns you can look at their browsing history. Be sure to know about any password protected sites they may be accessing and ask them to share their login details with you.
Be open - Encourage your child to be open about what they are doing online and who they are socialising with. Promote a culture of safety within the home and talk about the possible dangers which exist.
Protect your family - Use parental control on sites you don't want your child looking at as part of your online security product - it's an easy way to avoid disaster.