Can't upload attachments to issues or issue comments in Safari 26 on Mac

[fancyham]

🏷️ Discussion Type

Bug

💬 Feature/Topic Area

Issues

Body

I can't paste, drag and drop attachments (images, movies), nor click to add files into github issues.

Instead of uploading the file, it gets stuck at
<!-- Uploading "image.png"... —>
and never finishes uploading nor does it ever resolve to an image link on github.com/user-atachments like it should.

This is related to this same issue reported earlier, which we figured out a fix for at the time, but that fix no longer works and the bug returned:

• macOS 12.7.6, Safari 17.6: Uploading images to an issue post does not work (closing comment tag is altered) #181341

The old issues UI's comment fields can successfully upload attachments. For example, I can upload images successfully to this particular issue.

It has something to do with the new issues UI that rolled out last year in 2025.

To try to solve this, I cleared all 'website data'/cookies in Safari and deleted as many Safari support files in ~/Library as I could find: ~/Library/Containers/com.apple.safari
~/Library/Safari
~/Library/Preferences/com.apple.safari.plist
… but that didn't help. Still can't upload files,

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