According to The Register, lots of Amazon Echo devices were accidentally triggered by a presenter saying 'Alexa ordered me a dollhouse'.

Telly station CW-6 said the blunder happened during a Thursday morning news package about a Texan six-year-old who racked up big charges while talking to an Echo gadget in her home. According to her parents' Amazon account, their daughter said: "Can you play dollhouse with me and get me a dollhouse?" Next thing they knew, a $160 KidKraft Sparkle Mansion dollhouse and four pounds of sugar cookies arrived on their doorstep.
During that story's segment, a CW-6 news presenter remarked: "I love the little girl, saying 'Alexa ordered me a dollhouse'."
That, apparently, was enough to set off Alexa-powered Echo boxes around San Diego on their own shopping sprees. The California station admitted plenty of viewers complained that the TV broadcast caused their voice-controlled personal assistants to try to place orders for dollhouses on Amazon.

Voice purchasing seems to be enabled by default on the Echo, if you have 1-Click Purchasing set up.
How can I stop Alexa from ordering things if an advertisement or TV show says the words "Alexa, order ____"?
Will I need to disable voice purchasing altogether, or is there another way of making Alexa only respond to my orders?

Interesting, even though I have 1-Click purchasing activated my voice purchasing options have been deactivated by default. I have to actually activate them to buy stuff.

Currently Alexa cannot discern between different voices.



Either way there is the option to enable an optional confirmation code that can be set to be required for voice purchasing. (Settings > Voice Purchasing)


  (Optional) Require confirmation code
  Enter a 4-digit code, and then select Save Changes. Before you complete a purchase, Alexa asks for your code. The code does not appear in your voice history.
  
  Note: Make sure to create a code that you do not use for other accounts and services.


(Amazon Help)
