Steps to reproduce

1. First attach an image to a new Confluence page
2. Next, create the following markup in the page:

   !spaceKey:PageTitle^ImageName.gif|width="606"!
   

   Screenshot

3. The image will be displayed as usual
4. However, when you edit the page again and do some roundtrips (Wiki-markup -> Rich Text editor), the Wiki Markup becomes:

   !spaceKey:PageTitle^ImageName.gif|width=606"606"!
   

   Screenshot

5. More round-trips causes more duplicate values for the width parameter:

   !spaceKey:PageTitle^ImageName.gif|width=606"606""606""606"!
   

6. At this point, you are still allowed to edit and save the page.
7. However, when there's a page title change, you are not allowed to save the page anymore. You will get an Oops page with the following error:

   org.w3c.dom.DOMException: INVALID_CHARACTER_ERR: An invalid or illegal XML character is specified.
       at org.apache.xerces.dom.CoreDocumentImpl.createAttribute(Unknown Source) 
   

   • Screenshots:
     RenamingPage.png
     AfterRenamingRichText.png
     AfterSaving.png
8. You are also not allowed to switch to Wiki Markup editor to fix the markup.
   CantAccessWikiMarkup.png

Workaround

1. Don't use the quotes for the value. For example:

   !spaceKey:PageTitle^ImageName.gif|width=606!