Issue Summary

The intermittent issue, Portal-only Customers are not able to upload images using the Attachment field (dynamic field coming from add-on Extension for Jira Service Management).
Error: 'Unfortunately, you do not have permission to create attachments'.

Steps to Reproduce

1. install the add on from here
2. create a portal only customer in your test instance
3. In one of the request types, remove the field default attachment field (if there is any) and add the same from 'Customer Form Extension'.
   
4. Now login from the portal only customer account and you will see that you are not able to upload the attachments.
   
5. If you add the default attachment field in the request form then it works fine with the same permissions.

Expected Results

The customer should be able to upload the files for the dynamic field as well.

Actual Results

Error: 'Unfortunately, you do not have permission to create attachments'.

Workaround

1.Clear the browser cache and cookies,  or
2.Use the native Attachment field instead of the dynamic field