IMG_2139Shoppers who want to grab deals as fast as they possibly can now have a new tool at their disposal: Amazon’s app for the iPhone now lets users sign into their accounts using an iPhone’s Touch ID fingerprint sensor. The new capability comes courtesy of an update released this week to take advantage of new developer tools in iOS 8.

There’s one hitch: nobody seems to know how to turn the feature on, or off. When I opened up my Amazon app and navigated to my account page after the update yesterday, it asked me to enter my password. After that, I tried to do things that I thought would trigger the Touch ID login, but nothing worked. There’s no toggle switch in the app’s settings to turn it on or off, and nobody else on the internet seems to know how it works either.

All of the other articles I’ve read about Amazon’s new feature have pointed out that the company added it, but none of them include instructions about how to toggle it. A representative for Amazon didn’t respond to a request for comment about what sets it off, either.

This is easily one of the most bizarre roll-outs of a new feature as critical to security as Touch ID. If Amazon enables it by default and doesn’t include a way to disable it, that means people who have the Amazon iPhone app are putting themselves at risk of letting an attacker with their device access their Amazon account if that attacker is able to replicate their fingerprint.

Still, when the functionality works, it could be a potential game-changer for people interested in buying stuff from Amazon. Over the past year, I’ve become slightly more likely to buy apps from the App Store on my iPhone just because it’s super easy for me to get some new software with just my thumbprint. If Amazon can tap into some of that as well, it could prove very lucrative.

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