/usr/share/mozilla/extensions/ is in xul-ext-ublock-origin 1.6.6+dfsg-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/mozilla/extensions/{3550f703-e582-4d05-9a08-453d09bdfdc6}/
/usr/share/mozilla/extensions/{3550f703-e582-4d05-9a08-453d09bdfdc6}/uBlock0@raymondhill.net
/usr/share/mozilla/extensions/{8de7fcbb-c55c-4fbe-bfc5-fc555c87dbc4}/
/usr/share/mozilla/extensions/{8de7fcbb-c55c-4fbe-bfc5-fc555c87dbc4}/uBlock0@raymondhill.net
/usr/share/mozilla/extensions/{92650c4d-4b8e-4d2a-b7eb-24ecf4f6b63a}/
/usr/share/mozilla/extensions/{92650c4d-4b8e-4d2a-b7eb-24ecf4f6b63a}/uBlock0@raymondhill.net
/usr/share/mozilla/extensions/{aa3c5121-dab2-40e2-81ca-7ea25febc110}/
/usr/share/mozilla/extensions/{aa3c5121-dab2-40e2-81ca-7ea25febc110}/uBlock0@raymondhill.net
/usr/share/mozilla/extensions/{ec8030f7-c20a-464f-9b0e-13a3a9e97384}/
/usr/share/mozilla/extensions/{ec8030f7-c20a-464f-9b0e-13a3a9e97384}/uBlock0@raymondhill.net