[mark-t]

I've never come across a keypad lock that would be vulnerable to this. You either have to press # at the end of the code, or the codes are significantly longer than 4 digits. Of course, even in the first category, entering 24 codes (50% chance of entering 12 or fewer) isn't a huge barrier once you know the four digits.

[icefox]

I want to say that a bunch of cars had this. Even worse each button did 2 numbers so rather then 10 numbers there was actually only 5.

[thaumaturgy]

One of my security-conscious clients has just had electronic locks installed on two different R&D buildings.

Neither of them require a special digit after the code, or an enter key, and both of them have entry codes with repeating digits.