ISPConfig language_edit.php PHP Code Injection

This module exploits a PHP code injection vulnerability in ISPConfig's
language_edit.php file. The vulnerability occurs when the `admin_allow_langedit`
setting is enabled, allowing authenticated administrators to inject arbitrary
PHP code through the language editor interface.

This module will automatically check if the required `admin_allow_langedit`
permission is enabled, and attempt to enable it if it's disabled (requires
admin credentials with system configuration access).

The exploit works by injecting a PHP payload into a language file, which
is then executed when the file is accessed. The payload is base64 encoded
and written using PHP's file_put_contents function.