/usr/share/postgresql/9.3/extension/ is in postgresql-9.3-postgis-scripts 2.1.2+dfsg-2.
This file is owned by root:root, with mode 0o755.
..
/usr/share/postgresql/9.3/extension/postgis--2.0.0--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis--2.0.1--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis--2.0.2--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis--2.0.3--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis--2.0.4--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis--2.1.0--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis--2.1.0rc1--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis--2.1.0rc2--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis--2.1.0rc3--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis--2.1.1--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis--2.1.2--2.1.2next.sql
/usr/share/postgresql/9.3/extension/postgis--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis--2.1.2next--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis--unpackaged--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis.control
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.0.0--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.0.1--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.0.2--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.0.3--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.0.4--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.1.0--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.1.0rc1--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.1.0rc2--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.1.0rc3--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.1.1--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.1.2--2.1.2next.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--2.1.2next--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder--unpackaged--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_tiger_geocoder.control
/usr/share/postgresql/9.3/extension/postgis_topology--2.0.0--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology--2.0.1--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology--2.0.2--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology--2.0.3--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology--2.0.4--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology--2.1.0--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology--2.1.0rc1--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology--2.1.0rc2--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology--2.1.0rc3--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology--2.1.1--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology--2.1.2--2.1.2next.sql
/usr/share/postgresql/9.3/extension/postgis_topology--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology--2.1.2next--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology--unpackaged--2.1.2.sql
/usr/share/postgresql/9.3/extension/postgis_topology.control