Not sure what the difference between the "CODE" tag and the "CODEBOX" tag is, but spoiler tags are still executed in the "codebox" tag. It works fine in the "CODE" tag, but that tag isn't readily available when posting.
Example:
CODE
Just out of curiosity:
CODEbold text
Example:
CODE
spoiler text
Code:
[spoiler]spoiler text[/spoiler]
Just out of curiosity:
CODEbold text