/usr/share/squirrelmail/plugins/quicksave/ is in squirrelmail-quicksave 2.4.5-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/squirrelmail/plugins/quicksave/common_functions.php
/usr/share/squirrelmail/plugins/quicksave/config.php
/usr/share/squirrelmail/plugins/quicksave/config_default.php
/usr/share/squirrelmail/plugins/quicksave/config_example.php
/usr/share/squirrelmail/plugins/quicksave/functions.php
/usr/share/squirrelmail/plugins/quicksave/index.php
/usr/share/squirrelmail/plugins/quicksave/locale/
/usr/share/squirrelmail/plugins/quicksave/locale/.htaccess
/usr/share/squirrelmail/plugins/quicksave/locale/getpot
/usr/share/squirrelmail/plugins/quicksave/locale/index.php
/usr/share/squirrelmail/plugins/quicksave/locale/quicksave.pot
/usr/share/squirrelmail/plugins/quicksave/login_functions.php
/usr/share/squirrelmail/plugins/quicksave/setup.php
/usr/share/squirrelmail/plugins/quicksave/templates/
/usr/share/squirrelmail/plugins/quicksave/templates/default/
/usr/share/squirrelmail/plugins/quicksave/templates/default/index.php
/usr/share/squirrelmail/plugins/quicksave/templates/default/motd_recover_alert.tpl
/usr/share/squirrelmail/plugins/quicksave/templates/index.php