Redaxo CMS Mediapool Addon < 5.5.1 - Arbitrary File Upload

# Exploit Title: Redaxo CMS Mediapool Addon < 5.5.1 - Arbitrary File Upload
# Date: 2018-06-13
# Exploit Author: mn@HackerWerkstatt
# Vendor Homepage: https://redaxo.org
# Software Link: https://redaxo.org/download/redaxo/5.5.1.zip
# Version: 5.5.1 and older
# Tested on: LinuxMint
# More: Login required

### PoC ###

In the REDAXO CMS under version 5.6.0 the mediapool addon is vuln. Users who have an user-account, like editor, 
can use the mediapool to upload files. The mediapool addon under version 2.4.0 uses a blacklist for fileupload. 
For users it isn't possible upload files named: php, php4, php5, php6 or php7.

But, if you name the files like php71 or php53 the blacklist-function ignore this and upload of shellcode-file is possible.

https://example.com/redaxo/index.php?page=mediapool/media

### Fixed in mediapool 2.4.0 and Redaxo CMS 5.6.0
### reported: 08.03.2018
### fixed: 08.06.2018