The suffix used by the webdav interface (ezwebdavcontentbackend.php line 1533 approx) is wrong when the file is uploaded using the multiupload extension.

The suffix is set to: var/ezwebin_site/storage/original/application/fabe25cd0161cccd9ee095c2179a15cb

which is the storage path of the file.

The issue might be that there is a missing suffix in the storage directory when files are being uploaded via multiupload. As ls of my storage folder indicates the files uploaded via mu are missing the .php extension:

bash-3.2# pwd
/www/ezpublish-4.1.2/var/ezwebin_site/storage/original/application
bash-3.2# ls -la
total 240
drwxrwxrwx 6 daemon admin 204 Jun 2 11:15 .
drwxrwxrwx 3 daemon admin 102 May 28 13:32 ..
rw-rr- 1 daemon admin 72 Jun 1 13:14 048e730e174fc8e7bbd38a7e85326f9d.php
rw-rw-rw 1 daemon wheel 171 Jun 1 13:12 ed91b1cf82b77d406758a020242f6093
rw-rw-rw 1 daemon wheel 839 Jun 2 11:15 fabe25cd0161cccd9ee095c2179a15cb
rw-rr- 1 daemon admin 107847 Jun 2 10:48 fe1653a23ea23ac0613d09936c766193.php

Steps to reproduce

Upload a file (e.g. a .php file) via the multiupload interface
Connect via webdav to the folder where the file is located
Notice that the display name used in WebDAV is the md5 sum that comes from the stored file.