/usr/lib/gnumeric/1.12.28/plugins/ is in gnumeric-plugins-extra 1.12.28-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/gnumeric/1.12.28/plugins/gnome-glossary/
/usr/lib/gnumeric/1.12.28/plugins/gnome-glossary/glossary-po-header
/usr/lib/gnumeric/1.12.28/plugins/gnome-glossary/gnome_glossary.py
/usr/lib/gnumeric/1.12.28/plugins/gnome-glossary/plugin.xml
/usr/lib/gnumeric/1.12.28/plugins/paradox/
/usr/lib/gnumeric/1.12.28/plugins/paradox/paradox.so
/usr/lib/gnumeric/1.12.28/plugins/paradox/plugin.xml
/usr/lib/gnumeric/1.12.28/plugins/perl-func/
/usr/lib/gnumeric/1.12.28/plugins/perl-func/perl_func.pl
/usr/lib/gnumeric/1.12.28/plugins/perl-func/plugin.xml
/usr/lib/gnumeric/1.12.28/plugins/perl-loader/
/usr/lib/gnumeric/1.12.28/plugins/perl-loader/perl_loader.so
/usr/lib/gnumeric/1.12.28/plugins/perl-loader/plugin.xml
/usr/lib/gnumeric/1.12.28/plugins/py-func/
/usr/lib/gnumeric/1.12.28/plugins/py-func/plugin.xml
/usr/lib/gnumeric/1.12.28/plugins/py-func/py_func.py
/usr/lib/gnumeric/1.12.28/plugins/python-loader/
/usr/lib/gnumeric/1.12.28/plugins/python-loader/plugin.xml
/usr/lib/gnumeric/1.12.28/plugins/python-loader/python_loader.so
/usr/lib/gnumeric/1.12.28/plugins/python-loader/ui-console-menu.xml