/usr/share/mozilla/extensions/{3550f703-e582-4d05-9a08-453d09bdfdc6}/{F8147CF4-B9E3-445B-AA87-081ED66548F8} is in xul-ext-dispmua 1.6.8-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/mozilla/extensions/{3550f703-e582-4d05-9a08-453d09bdfdc6}/../../../xul-ext/dispmua