Hi Bram,
Thank you for reporting this. May I ask what type of taxonomy is that, and if you use any shortcode/taxonomy related plugins? I have tried to add the shortcode to a category description, and it is not executed.
I believe WordPress by default does not execute those shortcodes on the back-end. In case you have a custom plugin/custom code that allows that, let me know, so I can replicate the issue.
Thank you!