Real Player 16.0.3.51 - 'external::Import()' Directory Traversal to Remote Code Execution (RCE)

# Exploit Title: Real Player 16.0.3.51 - 'external::Import()' Directory Traversal to Remote Code Execution (RCE)
# Google Dork: n/a
# Date: May 31, 2022
# Exploit Author: Eduardo Braun Prado
# Vendor Homepage: http://real.com/
# Software Link: http://real.com/
# Version: ver. 16.00.282, 16.0.3.51, Cloud 17.0.9.17, v.20.0.7.309
# Tested on: Windows 7, 8.1, 10
# CVE : N/A

PoC: https://github.com/Edubr2020/RP_Import_RCE/raw/main/RP_Import_RCE.zip
vídeo: https://youtu.be/CONlijEgDLc

Real Player uses Microsoft Internet Explorer functionality and exposes properties and methods through a special mean which is application specific:

The 'external' object and it exposes several custom methods and properties.

The 'Import()' method is handled in unsafe way regarding the 'Copy to My Music' parameter, which allows for arbitrary file types downloading
which could be unsafe as only audio/image/video types should be allowed to download to the user´s disk. Additionally it does not properly sanitize file paths
allowing planting of arbitrary files on arbitrary locations. Even though it displays an error because it cannot render the downloaded file, the file remains until the user
closes the dialog box. Additionally when opening new windows, Real Player looks for an old, obsolete IE library (shdoclc.dll), which can also be abused to run code automatically without needing to wait
until reboot (true when file is planted in 'startup' folder).

The attacker needs to host the files to be copied/downloaded in an SMB or WebDav share.
The directory 'appdata' must be placed in the share's root.

The PoC will drop 'shdoclc.dll' (has simple code to run 'cmd.exe' at 'DllMain()' for demonstration purposes)  to the user´s 'windowsapps' folder and 'write.exe' to 'startup' folder, so it works universally (any Windows version from at least XP up to 11)

tested on RP ver. 16.00.282, 16.0.3.51, Cloud 17.0.9.17, v.20.0.7.309