Not able to upload csv file in chained select

I am not being able to upload a csv file in chained select add-on. I get the message “There was an error processing this file. Error: illegal extension, Message: Sorry, this file extension is not permitted for security reasons”.
I thought it was a restriction of the site, but I can upload the same file in the multimedia section.

What should I do?

Please open a support ticket here and we’ll be happy to help

Done. Looking forward to your response. Thanks Chris.