updated 07:23 pm EDT, Wed April 16, 2014
Similar technique used to unlock iPhone 5s can be used on Galaxy S 5
The Samsung Galaxy S5 is subject to the same fake fingerprint technique that the Apple iPhone 5s was, with an added danger -- users can attempt the fake finger on the fingerprint sensor as many times as possible for a success, with no passcode or two-factor authentication needed.
Security Research Labs documented the flaw on YouTube. It says of the flaw that "despite being one of the premium phone's flagship features, Samsung's implementation of fingerprint authentication leaves much to be desired. The finger scanner feature in Samsung's Galaxy S5 raises additional security concerns to those already voiced about comparable implementations."
Apple automatically disables its Touch ID system and reverts back to a passcode if the finger hasn't been used to unlock the iPhone within the last 48 hours, or after three unsuccessful tries. Thieves would have to obtain the iPhone and the fingerprint, obtain a copy of the correct finger used by the owner for unlocking, make a special mold of the owner's finger, and unlock the phone very quickly in order to defeat the security or the remote wiping feature.
While it should be noted that the chances of someone both stealing an iPhone and getting a usable print in order to make the mold is highly unlikely outside of espionage circles, the Samsung flaw has no such reversion -- and assuming the user does not remotely wipe the phone, thieves have an unlimited time to perform the hack.
Galaxy S5 fake finger technique
iPhone 5s procedure