/usr/lib/mozilla/extensions/{3550f703-e582-4d05-9a08-453d09bdfdc6}/kde5wallet@guillermo.molina is in xul-ext-kwallet5 1.3-1ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/mozilla/extensions/{3550f703-e582-4d05-9a08-453d09bdfdc6}/../../../xul-ext/kwallet5