Images of imported XAR broken

On XWiki 5.3 importing an exported XAR file from another installation breaks image attachments. They are only shown partially, see attached screenshots.

I have two installations:
5.3 Standalone on Windows Server 2003
5.3 WAR installation (MySQL 5.5.34, Tomcat 7.0.42) on Windows XP

This issue occurs everytime I import exported XAR files, even from standalone to standalone.

Steps to reproduce:
1. Go to wiki administration
2. Export wiki
3. Go to 2nd environment
4. Import the XAR
>> Images are broken