Sorry, this file extension is not permitted for security reasons

[zhihenglin1998 (Zhiheng Lin)]

I do not have any extension limit set, but the upload widget still does not allow me to upload any spreadsheet. xls, csv, xlsx all do not work, PDFs are fine though.

I have added the following into wp-config: define(‘ALLOW_UNFILTERED_UPLOADS’, true);

[chrishajer (Chris (Gravity Forms))]

Gravity Forms is not preventing those uploads. It’s either WordPress or something on your server (like a security module.) I would first try eliminating any WordPress restrictions using a plugin such as this one:

WP Extra File Types

Let us know how that turns out. Thank you.