The Lingering Injuries table in the DMG (p. 272) contains some wounds that can only be fixed by powerful healing magic, for instance:
Horrible Scar. You are disfigured to the extent that the wound cannot be easily concealed. You have disadvantage on Charisma (Persuasion) checks and advantage on Charisma (Intimidation) checks. Magical healing of 6th level or higher, such as heal and regenerate, removes the injury.
Can the necessary magical healing described here be a lower-level spell (such as cure wounds) that is upcast to 6th level? Or must it be a healing spell that is already 6th level or above before upcasting?