If you download (content/download) files upload with multiupload extension, the content-type of those files won't be correct.

Steps to Reproduce

1. Create a simple text file and name it "some_file_001.txt"
2. Triplicate that file and create "some_file_003.txt" and "some_file_003.txt"
3. Upload them all with multiupload
4. Duplicate again "some_file_001.txt" and create "some_file_004.txt"
5. Open the media content part and create a file content object. Add "some_file_004.txt" to it and publish it
6. Download one of the multiuploaded files with curl -i "http://your_site.com/content/download/140/863/file/some_file_001.txt"
7. Download the singleuploaded file with curl -i "http://your_site.com/content/download/140/863/file/some_file_004.txt"
8. Confirm your results will look like the one below

curl -i "http://your_site.com/content/download/140/863/file/some_file_001.txt

HTTP/1.1 200 OK
Date: Wed, 03 Dec 2014 11:02:49 GMT
Server: Apache/2.2.22 (Debian)
X-Powered-By: eZ Publish
Expires: Wed, 03 Dec 2014 11:12:49 GMT
Last-Modified:
Cache-Control:
Pragma:
Served-by: 530.ezp.pt
Content-language: en-GB
Content-Disposition: attachment
Content-Length: 945949
Content-Transfer-Encoding: binary
Accept-Ranges: bytes
Content-Type: application/octet-stream

curl -i "http://your_site.com/content/download/140/863/file/some_file_004.txt

HTTP/1.1 200 OK
Date: Wed, 03 Dec 2014 11:02:16 GMT
Server: Apache/2.2.22 (Debian)
X-Powered-By: eZ Publish
Expires: Wed, 03 Dec 2014 11:12:16 GMT
Last-Modified:
Cache-Control:
Pragma:
Served-by: 530.ezp.pt
Content-language: en-GB
Content-Disposition: attachment
Content-Length: 947601
Content-Transfer-Encoding: binary
Accept-Ranges: bytes
Vary: Accept-Encoding
Content-Type: text/plain