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.

In egroupware version 26.0 and earlier, an authenticated administrator ...

EGroupware has Authenticated RCE via Malicious eTemplate Upload