Issue Summary

Intermittently, uploads on attachment page doesn't work. Attaching a file will result in the page refreshing, but the new file will not show up. We see a 403 error in the developer tool's network tab.

Steps to Reproduce

(Intermittent)

1. On a page with old editor (TinyMCE), add the "Attachment" macro
2. Try to upload files. Size of attachment doesn't matter. Method of upload (drag & drop VS pick from file explorer) doesn't matter.

Expected Results

Attachment list includes the newly uploaded file upon refresh

Actual Results

File does not get uploaded

403 error in network tab for POST request against https://<site-name>.atlassian.net/wiki/pages/plugins/attachments/doattachfile.action?pageId=<pageID>

Workaround

Continue using old editor page: Upload the file again. Usually, problem goes away upon second try.
OR
Make a copy of the page using the new editor (fabric), the problem shouldn't happen with "Attachment" macro on new editor page.