/etc/ is in roundcube-plugins 1.2~beta+dfsg.1-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/etc/roundcube/
/etc/roundcube/plugins/
/etc/roundcube/plugins/emoticons/
/etc/roundcube/plugins/emoticons/config.inc.php
/etc/roundcube/plugins/http_authentication/
/etc/roundcube/plugins/http_authentication/config.inc.php
/etc/roundcube/plugins/enigma/
/etc/roundcube/plugins/enigma/config.inc.php
/etc/roundcube/plugins/managesieve/
/etc/roundcube/plugins/managesieve/config.inc.php
/etc/roundcube/plugins/password/
/etc/roundcube/plugins/password/config.inc.php
/etc/roundcube/plugins/new_user_identity/
/etc/roundcube/plugins/new_user_identity/config.inc.php
/etc/roundcube/plugins/newmail_notifier/
/etc/roundcube/plugins/newmail_notifier/config.inc.php
/etc/roundcube/plugins/database_attachments/
/etc/roundcube/plugins/database_attachments/config.inc.php
/etc/roundcube/plugins/zipdownload/
/etc/roundcube/plugins/zipdownload/config.inc.php
/etc/roundcube/plugins/help/
/etc/roundcube/plugins/help/config.inc.php
/etc/roundcube/plugins/acl/
/etc/roundcube/plugins/acl/config.inc.php
/etc/roundcube/plugins/additional_message_headers/
/etc/roundcube/plugins/additional_message_headers/config.inc.php
/etc/roundcube/plugins/squirrelmail_usercopy/
/etc/roundcube/plugins/squirrelmail_usercopy/config.inc.php