Authenticated RCE via Malicious eTemplate Upload in EGroupware

In egroupware version 26.0 and earlier, an authenticated administrator can achieve OS-level Remote Code Execution (RCE) by uploading a malicious eTemplate XML file (.xet) to the VFS /etemplates mount. The Widget::expand_name() method passes template widget attribute values directly into a PHP eval() call with only double-quote escaping applied - backtick characters are not escaped. In PHP, backticks inside a double-quoted eval() string execute shell commands. This allows an admin-level user to escalate from web application access to arbitrary OS command execution on the server.