/usr/lib/iceweasel/browser/defaults is in iceweasel 38.8.0esr-1~deb7u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/iceweasel/browser/../../../share/iceweasel/browser/defaults
/usr/lib/iceweasel/browser/../../../share/iceweasel/browser/defaults