The user can enter 4 digits as the month value in the expiration date field.

[Svyatoslavik]

Steps to reproduce

1. enter a credit card number, example 5555 5555 5555 4444
2. enter a expiration date 11/22
3. switch cursor back to month field in expiration date
4. now you can enter 4 digits as a month value

Screenshots

[aldarund]

They can even enter 11002/2