Here are the following steps on how to reproduce this bug:

1. Go to any space and create a new page
2. Attach the following PPT file (with special characters)
   Unable to embed resource: Chinese_Character_Garbled.ppt of type application/vnd.ms-powerpoint
3. Edit the page
4. Insert "Other Macros" -> Choose "Office Powerpoint" -> Select the file just uploaded -> Save it
5. Wait for a few seconds for the Powerpoint slides presentation to load
6. Special characters are garbled

I am not sure if this is a Confluence or an Office Connector problem. If this is an Office Connector problem, I will move this bug to OFFCONN project.