CVE-2020-15680
If a valid external protocol handler was referenced in an image tag, the resulting broken image size could be distinguished from a broken image size of a non-existent protocol handler. This allowed an attacker to successfully probe whether an external protocol handler was registered. This vulnerability affects Firefox < 82. Date published : 2020-10-22 https://bugzilla.mozilla.org/show_bug.cgi?id=1658881