Every time the game starts I get this error. I finally did a little bit of sleuthing to determine what AddOn was causing the error and unfortunately it was Carbonite. I ran the following command to start Taint Logging.

/console taintLog 1

Reloaded the interface and waited for the error. Once the error occurred I exited the game an d opened the Log. Here is what it held.

taint.log

The error seems to be:
12/12 00:08:01.441 Execution tainted by Carbonite while reading Nx - Interface\AddOns\Carbonite.Quests\NxQuest.lua:1896 QuestOptions()

This is on the Macintosh version of WoW Classic.
Hope this helps!

Same as #111. Just update from this repo.