Parents are being urged to be extra vigilant around children's high-tech toys.
So-called 'smart' toys and gadgets are often fitted with technology that connects to the internet or Bluetooth, which can put users at risk of hacking.
British consumer group Which? studied 15 devices and found that eight were vulnerable to hacking.
Tech reporter Jess Kelly says that while parents shouldn't panic, they should be aware of the risks.
"It's not necessarily that they're going to do anything bad with this information, but there is a slight exploitation there," she said.
"For example, if you have a four-year-old with a doll, that can listen in to your child's conversations.
"They can record information and perhaps send marketing activity or ads or whatever it is, tailored to whatever your child is interested in."