How to get SpellBad highlighting under the cursor?

[Lifepillar]

Is there a way in Vim Script to get the highlighting under the cursor
when it is SpellBad or similar group?

For instance, after:

:new
:set ft=c
:set spell
i// Whaat?

I would like to determine that "Whaat" is highlighted with SpellBad.

I have tried with synIDattr(), but it always returns the attributes of
the underlying highlight group (Comment in the previous example).

Thanks,
Life.