/usr/share/mozilla/extensions/{ec8030f7-c20a-464f-9b0e-13a3a9e97384}/elemhidehelper@adblockplus.org is in xul-ext-adblock-plus-element-hiding-helper 1.2.2-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/mozilla/extensions/{ec8030f7-c20a-464f-9b0e-13a3a9e97384}/../../../xul-ext/adblock-plus-element-hiding-helper