Issue Summary

 When a Confluence space is migrated cloud-to-cloud, comment bodies are re-written
and re-serialised during import. Attachment filenames stored in the comment
storage format as HTML-encoded entities (for example accented or umlaut
characters) are decoded to their Unicode equivalents as part of this process.
After migration, the embedded attachment in the comment renders a placeholder or
thumbnail, but cannot be opened. The attachment itself migrates successfully and
is present and openable from the page's attachment list.

Steps to Reproduce

1.  On the source Confluence Cloud site, create a page in a test space and upload
   an attachment whose filename contains non-ASCII characters (for example
   accented or umlaut characters).
2. Add a comment to that page and embed the uploaded attachment in the comment.
   Confirm the comment storage format contains the filename as HTML-encoded
   entities within the ri:attachment reference.

1. Migrate the space to the destination Confluence Cloud site using Transfer
   Confluence data.
2. On the destination site, open the migrated page and locate the migrated
   comment.
3. Click the embedded attachment thumbnail in the comment.
4. Expected Results

The attachment embedded in the comment renders correctly and opens in the
preview when clicked, matching the behaviour on the source site.
 

Actual Results

The attachment embedded in the comment does not open when clicked. The
attachment is present on the page and can be opened from the page's attachment
list. Inspecting the destination comment storage format shows the filename
decoded from HTML entities to Unicode characters.

Workaround

Currently there is no known workaround for this behavior. A workaround will be
added here when available