Image cannot be displayed when exporting a page with more than 50 images into Word file

Summary

Image cannot be displayed when exporting a page with more than 50 images into Word file

When using the Export to Word feature on a Confluence page that contains more than 50 images, the exported Word file cannot display all of the images properly or appears to be broken.

Environment

Confluence 6.11.2
Confluence 6.13.0

Steps to Reproduce

1. Create a new page in Confluence and upload 55 different image files into the page
   • They can be the same image, but they all must be different files
2. Save the Page and make sure all 55 images are displaying properly in the Confluence Page
3. Export the page into Word file

Expected Results

The exported Word file is able to display all 55 images properly

Actual Results

Any images that are after the 50th image will be broken.

• Broken Image exported from Confluence 6.11.2 viewed in Microsoft Word 2016:
  
• Broken Image exported from Confluence 6.13.0 viewed in Microsoft Word 2016:
  
• Broken Image is not displaying any error message in Office 365 Subscription on Mac OS X
• Exported result:
  Much+More+Image+Here.doc

Information

• This is the image file that is being used to test (file size around 2KB):
  
• Also performed the test with a larger image at around 2MB and same outcome is observed (images after the 50th starts to break)
• Turning the Logging and Profiling for Confluence to Diagnostic mode during the Word Export but no error messages are logged.

As the reason behind why the image breaks after the 50th image is not known yet, this bug might be encountered before or after 50 images depends on the environment.