/usr/share/mozilla/extensions/{92650c4d-4b8e-4d2a-b7eb-24ecf4f6b63a}/foxyproxy@eric.h.jung is in xul-ext-foxyproxy-standard 3.4-1.1~deb7u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/mozilla/extensions/{92650c4d-4b8e-4d2a-b7eb-24ecf4f6b63a}/../../../xul-ext/foxyproxy-standard