Since when is 'e' a valid hexidecimal number I'm seeing lots if questions with this as valid answer

Question

16 numbers in hex

Answer 1

Hmmm... you got sixteen digits in a hexadecimal system:
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F

If you are asking why it is a lowercase, well, it's been this way in the quizzes since a few updates ago.