Joomla Extension - getk2.org - Privileged RCE vulnerability in K2 extension for Joomla < 2.26

The K2 frontend article-attachment upload path accepts files whose extension is .php, and Apache's standard mod_php matches \.php$ and executes them under the K2 web user. A K2 Author can upload a shell.php, then fetch /media/k2/attachments/shell.php and execute arbitrary PHP code in the web server's context.