/usr/share/roundcube/plugins/zipdownload/ is in roundcube-plugins-extra 0.6-20111030.
This file is owned by root:root, with mode 0o755.
..
/usr/share/roundcube/plugins/zipdownload/config.inc.php
/usr/share/roundcube/plugins/zipdownload/config.inc.php.dist
/usr/share/roundcube/plugins/zipdownload/localization/
/usr/share/roundcube/plugins/zipdownload/localization/ca_ES.inc
/usr/share/roundcube/plugins/zipdownload/localization/cs_CZ.inc
/usr/share/roundcube/plugins/zipdownload/localization/da_DK.inc
/usr/share/roundcube/plugins/zipdownload/localization/de_CH.inc
/usr/share/roundcube/plugins/zipdownload/localization/de_DE.inc
/usr/share/roundcube/plugins/zipdownload/localization/en_GB.inc
/usr/share/roundcube/plugins/zipdownload/localization/en_US.inc
/usr/share/roundcube/plugins/zipdownload/localization/es_AR.inc
/usr/share/roundcube/plugins/zipdownload/localization/es_ES.inc
/usr/share/roundcube/plugins/zipdownload/localization/et_EE.inc
/usr/share/roundcube/plugins/zipdownload/localization/fr_FR.inc
/usr/share/roundcube/plugins/zipdownload/localization/gl_ES.inc
/usr/share/roundcube/plugins/zipdownload/localization/hu_HU.inc
/usr/share/roundcube/plugins/zipdownload/localization/it_IT.inc
/usr/share/roundcube/plugins/zipdownload/localization/nl_NL.inc
/usr/share/roundcube/plugins/zipdownload/localization/pl_PL.inc
/usr/share/roundcube/plugins/zipdownload/localization/pt_BR.inc
/usr/share/roundcube/plugins/zipdownload/localization/ro_RO.inc
/usr/share/roundcube/plugins/zipdownload/localization/ru_RU.inc
/usr/share/roundcube/plugins/zipdownload/localization/tr_TR.inc
/usr/share/roundcube/plugins/zipdownload/skins/
/usr/share/roundcube/plugins/zipdownload/skins/default/
/usr/share/roundcube/plugins/zipdownload/skins/default/zip.png
/usr/share/roundcube/plugins/zipdownload/zipdownload.js
/usr/share/roundcube/plugins/zipdownload/zipdownload.php