WordPress Concours 1.1 Cross Site Scripting

`Product: WordPress Concours Plugin - https://wordpress.org/plugins/wp-concours/  
Vendor: Olyos  
Tested version: 1.1  
CVE ID: CVE-2017-17719  
  
** CVE description **  
A cross-site scripting (XSS) vulnerability in the wp-concours plugin through 1.1 for WordPress allows remote attackers to inject arbitrary web script or HTML via the result_message parameter to includes/concours_page.php.  
  
** Technical details **  
In wp-concours/includes/concours_page.php:18, $_REQUEST['result_message'] is stored in the $message_str variable without proper sanitization. This variable is then echoed back to user on line 28.  
  
Vulnerable code:  
https://plugins.trac.wordpress.org/browser/wp-concours/trunk/includes/concours_page.php#L18  
  
** Proof of Concept **  
http://<host>/wordpress/wp-admin/admin.php?page=concours&result_message=<script>alert(document.cookie);</script>  
  
** Solution **  
No fix available yet.  
  
** Timeline **  
28/09/2017: vendor contacted; vendor asks for technical report  
06/10/2017: requested an update regarding the fix; vendor says in November  
05/12/2017: sent an e-mail to warn about the release of that advisory; no reply  
19/12/2017: report published  
  
** Credits **  
Vulnerability discovered by Nicolas Buzy-Debat working at Orange Cyberdefense Singapore (CERT-LEXSI).  
  
--  
Best Regards,  
  
Nicolas Buzy-Debat  
Orange Cyberdefense Singapore (CERT-LEXSI)  
_________________________________________________________________________________________________________________________  
  
Ce message et ses pieces jointes peuvent contenir des informations confidentielles ou privilegiees et ne doivent donc  
pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu ce message par erreur, veuillez le signaler  
a l'expediteur et le detruire ainsi que les pieces jointes. Les messages electroniques etant susceptibles d'alteration,  
Orange decline toute responsabilite si ce message a ete altere, deforme ou falsifie. Merci.  
  
This message and its attachments may contain confidential or privileged information that may be protected by law;  
they should not be distributed, used or copied without authorisation.  
If you have received this email in error, please notify the sender and delete this message and its attachments.  
As emails may be altered, Orange is not liable for messages that have been modified, changed or falsified.  
Thank you.  
  
  
  
`