The extension's cookie is set without the SameSite attribute

Firefox gives the following warning:

Cookie “cookie_optin” will be soon rejected because it has the “sameSite” attribute set to “none” or an invalid value, without the “secure” attribute. To know more about the “sameSite“ attribute, read https://developer.mozilla.org/docs/Web/HTTP/Cookies

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information