Does Hex stack with Hellish Rebuke?

[MarkVIIIMarc]

I am worried the damage of Hellish Rebuke is not an attack so my Warlock Tiefling can't add a D6 from Hex to the famage damage (if he makes the concentration save). Does Hex apply after Hellish Rebuke?

[Crgaston]

Nope. Hellish Rebuke is not an attack.

[RSP]

Hex requires an attack to add damage, whereas Hellish Rebuke works on a save, so Hex damage does not apply to HR.

Now Hexblades Curse would apply to HR, as it works on any damage roll.