Amazon Echo owners have been issued a security warning after a number in the United States automatically ordered dolls' houses being discussed on a TV show.
The high-tech gadgets have become a recent addition to hundreds of thousands of UK homes, after being one of the most popular presents at Christmas.
Owners can ask virtual assistant "Alexa" to carry out tasks, including internet shopping, using their voice as a command.
But a recent incident has shown that they are vulnerable to making potentially expensive mistakes.
Last week a San Diego TV station sparked complaints after a report about a girl who ordered a dolls' house via her parents' Amazon Echo caused devices in viewers' homes to also attempt to order dolls' houses.
The show depicted a 6-year-old asking her family's new Amazon Echo "can you play doll house with me and get me a doll house?"
The device followed the command, ordering a KidKraft Sparkle Mansion Dollhouse, in addition to "four pounds of sugar cookies".
The parents realised what had happened and have since added a code for purchases. They have also donated the dolls' house to a local children's hospital.
However, viewers' Alexa gadgets also complied with the request and also bought dolls' houses.
Voice-command purchasing is a default option on the Echo. Experts said the incident highlighted the need for people to password protect their Amazon Echos.
David Emm, a security expert at Kaspersky Labs, a web security firm, said: "People need to find a compromise where they feel comfortable between achieving security and enjoying the convenience of these gadgets. It is certainly advisable to opt for having a verbal password or code to minimise the risk."
He added that a growing wave of cyber criminals are targeting smart devices to hack into people's accounts.
Amazon did not respond to a request for a comment.