The YouTube clip, called "iPhone Unlock Without Passcode Glitch", depicts a user gaining access to a Touch ID-equipped device by first asking Siri what time it is.
When the spoken request brings up the time, the user taps on the clock face to reveal the World Clock screen and then selects the Timer icon at the bottom of the screen. He subsequently taps on the 'When Time Ends' option and presses the section that says 'Buy More Tones'.
Upon doing so, the Apple Store opens and the user presses the home button, which unlocks the phone without the user having typed in the passcode.
The video has been viewed over 420,000 times, with some iPhone owners thanking the video's creator for discovering the issue. However, repeated attempts by MacRumors have demonstrated that the method depicted does not allow "anyone" to access a passcode-protected iPhone.
Savvy users will have noted that the method only works because the user activates Siri by pressing the home button with a finger that has clearly already been registered with the Touch ID feature's fingerprint scanner. The same process undertaken using a fingerprint that isn't registered on your iPhone makes subsequent taps to "Buy More Tones" fail to open the iTunes Store.
So if you see anyone sharing the video, you can do them a favor by explaining that the video is misleading, and their phone's data remains safe and secure.