/usr/share/xscreensaver/config/ is in xscreensaver-data 5.30-1+deb8u2.
This file is owned by root:root, with mode 0o755.
..
/usr/share/xscreensaver/config/abstractile.xml
/usr/share/xscreensaver/config/cwaves.xml
/usr/share/xscreensaver/config/deco.xml
/usr/share/xscreensaver/config/distort.xml
/usr/share/xscreensaver/config/fiberlamp.xml
/usr/share/xscreensaver/config/fuzzyflakes.xml
/usr/share/xscreensaver/config/galaxy.xml
/usr/share/xscreensaver/config/hexadrop.xml
/usr/share/xscreensaver/config/m6502.xml
/usr/share/xscreensaver/config/metaballs.xml
/usr/share/xscreensaver/config/penrose.xml
/usr/share/xscreensaver/config/popsquares.xml
/usr/share/xscreensaver/config/ripples.xml
/usr/share/xscreensaver/config/shadebobs.xml
/usr/share/xscreensaver/config/slidescreen.xml
/usr/share/xscreensaver/config/swirl.xml
/usr/share/xscreensaver/config/tessellimage.xml
/usr/share/xscreensaver/config/xlyap.xml