She didn't ask for the expiration date

This is funny and all but first of all the guards could just say I don't know and they wouldn't even be lying.

Attention all Fortnite gamers: John Wick is in great danger and he needs your help to wipe out the squads in the Tilted Towers, but to do this he needs a golden scar and a couple of chug jugs. To help him, all he needs is your credit card number, the three digits on the back, and the expiration month and year. But, you gotta be quick, so John Wick can secure the bag and achieve the epic Victory Royal!

Workaround: interpret "and" as "plus", and say a single number which is the two summed together.

In the first frame which guard is lying? Seems like neither.

For those interested, ignoring the contradictory presentation of the riddle (as the knights themselves would not say the riddle since one always lies and one always tells the truth), the solution is simple. Ask the knights what the other knight would answer when asked what door is correct, and they will both say which path not to go to. Thus you pick the path that neither Knight says!

Logic:

Liar: Will say the wrong option, as they're being asked which door the truth telling knight would say (and they will lie about what the truth-teller would say)
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Truth-teller: Will say the wrong option, as they're being asked which door the liar would say (and they'll tell the truth about that)

NOTE: This can be expanded to a case with n doors by asking the knights to provide all the options that the other knight could say, and each will provide n-1 options, so you'd pick the one option that neither knight says. It is possible the liar may not list all options, but the truth-teller would, so the problem could still be worked out regardless (and you'd know which knight is the liar in that case).

Alternative answer: What's in your browser history?

Oooh! This is a great solution to this problem! Just write down both numbers and perform a luhn check:

https://en.wikipedia.org/wiki/Luhn_algorithm

The one that lies only has a 1 in 10 chance of making up a number that will pass the check! Cool shortcut: If it starts with a 1, 2, 7, 8, or 9, they're lying. Those are reserved for things that aren't credit cards 👍

This kinda falls apart with the knights talking at the start. Either there is 1 that only tells truth with the other not being bound by those rules or one that only tells lies with the other one doing whatever since one of those 2 is telling a lie.

For those interested, ignoring the contradictory presentation of the riddle (as the knights themselves would not say the riddle since one always lies and one always tells the truth), the solution is simple. Ask the knights what the other knight would answer when asked what door is correct, and they will both say which path not to go to. Thus you pick the path that neither Knight says!

Logic:

Liar: Will say the wrong option, as they're being asked which door the truth telling knight would say (and they will lie about what the truth-teller would say)
------------------------------------------
Truth-teller: Will say the wrong option, as they're being asked which door the liar would say (and they'll tell the truth about that)

NOTE: This can be expanded to a case with n doors by asking the knights to provide all the options that the other knight could say, and each will provide n-1 options, so you'd pick the one option that neither knight says. It is possible the liar may not list all options, but the truth-teller would, so the problem could still be worked out regardless (and you'd know which knight is the liar in that case).

Am I mistaken for recalling that in the original riddle, the question should have a boolean outcome (yes/no)?

Having a question with a big domain makes it a lot easier to guess what is a false and true outcome.

The easiest solution is to ask what is the color of their capes that they are wearing