/usr/share/pixmaps/iceweasel.png is in iceweasel 38.8.0esr-1~deb7u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/pixmaps/../iceweasel/browser/chrome/icons/default/default48.png
/usr/share/pixmaps/../iceweasel/browser/chrome/icons/default/default48.png