Police are warning parents to disable Snapchat's new mapping feature in their kids' phones.
"Snapchat has introduced a map feature that lets users track other people's location in real time, raising concerns among safety and privacy advocates," Constable Pete* wrote on the Waikato police Facebook page.
"Snap Map plots users and their snaps onto a map so friends and other Snapchatters can see where they are and what they are doing."
The location is so accurate, a technology journalist writing for The Verge was able to guess a friend's home address based on what Snapchat was telling her.
Const Pete said he's spent the past two weeks in a secondary school, and "98 percent" of the students use the messaging app.
"For those parents whose children have Snapchat, it might also be a good time to talk to them to ensure they understand the risks of allowing people to see their locations," said Waikato police.
Snapchat says users' locations are not shared until they turn on Snap Map, by turning on the camera and pinching inwards.
But once it's turned on, even if by accident, Snapchat will broadcast your location every time you open the app - even if it's just to look at messages others have sent.
"It's worrying that Snapchat is allowing under-18s to broadcast their location on the app where it can potentially be accessed by everyone in their contact lists," UK organisation the National Society for the Protection of Children said at the weekend.
"With public accounts, this will include those who are not known to the user. This highlights why it's vital children are automatically offered safer accounts on social media to ensure they are protected from unnecessary risks."
'Ghost mode' lets you look at others' locations without broadcasting your own.
"If you don't want people knowing where you live and the places you go to throughout the day, we strongly suggest you switch it to 'ghost mode'," said Const Pete.
New Zealand's NetSafe has a guide for parents on how to enable and disable different Snapchat features, including Snap Map.
Much of the concern comes from Snapchat's overwhelmingly young userbase. According to figures released by the company earlier this year, nearly three-quarters of the app's 161 million daily users are Millennials or younger.
"We all know with the growth in technology and the continual updates on apps these days privacy is difficult thing to keep a hold of, but you can take steps to reduce how much private information you share," said Const Pete.
Snapchat says users' locations disappear from the map if they haven't opened the app in eight hours.
* Newshub has requested Constable Pete's full name from Waikato police.