On Extranet, where we have page IDs that go above the 32-bit area, drag-n-drop upload of attachments can sometimes attach dropped files to the wrong page.

For example, earlier today I attached some files to the 'Test page' in my personal space, page ID: 69518087748091042. They were uploaded to the 'Security Cards' page in the 'Admin' space, page ID: 69518087748071009.

So the attachments page URLs are:

https://extranet.atlassian.com/pages/viewpageattachments.action?pageId=69518087748091042 – intended page
https://extranet.atlassian.com/pages/viewpageattachments.action?pageId=69518087748071009 – actual page

I imagine this is due to incorrect handling of page IDs in the JavaScript code, where we cast the value to a number. Page IDs need to always be treated as strings in JavaScript to avoid this truncation problem.