I suspect it's a Hey-wide thing.

But if you trim off the `?disposition=attachment` from the URL, it loads in the browser. At least for me in Firefox.

Ah... that makes sense. I hadn't heard of Hey before but it appears Hey World is a pretty newly added feature to a platform primarily built for & around email - attachments do make some deal of sense in that context, though I'd imagine I might still like to browse image attachments in my email client from time to time rather than stash them in downloads.

Might just be teething issues for a new product though.