Steps to reproduce

1. Go to Demonstration Space in Confluence 3.5.x
2. Browse to this blog-post: "Movember at Atlassian - Oooo we're half way there, oooooo oh..."
3. Edit the page/blog and add the link to an image attached to it in wiki markup editor:

   [^MoOfTheWeek.png]
   

4. Upgrade to 4.0
5. The link will be greyed out and no longer working

Workaround

Edit the page/blog, remove the link and re-add it.

Finding

• XHTML of the migrated content:

  <ac:link>
  	<ri:attachment ri:filename="MoOfTheWeek.png">
  		<ri:page ri:content-title="Movember at Atlassian - Oooo we're half way there, oooooo oh..." ri:space-key="ds" />
  	</ri:attachment>
  </ac:link>
  

  • If I edit the migrated XHTML to be like this, it works:

    <ac:link>
    	<ri:attachment ri:filename="MoOfTheWeek.png">
    		<ri:blog-post ri:posting-day="2011/02/08" ri:content-title="Movember at Atlassian - Oooo we're half way there, oooooo oh..." ri:space-key="ds" />
    	</ri:attachment>
    </ac:link>
    

• XHTML of the new re-added link:

  <ac:link>
  	<ri:attachment ri:filename="MoOfTheWeek.png" />
  </ac:link>
  

If you are upgrading to any versions after 4.0.3

Make sure to upgrade first, to 4.0.3, ensure all blogposts are migrated correctly (else, rerun the migration in 4.0.3), before upgrading to the version of your choice. (This is fixed only in 4.0.3's wiki to xhtml migration)