/usr/share/mozilla/extensions/{3550f703-e582-4d05-9a08-453d09bdfdc6}/{58D4392A-842E-11DE-B51A-C7B855D89593} is in xul-ext-compactheader 2.0.8-1.
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/compactheader