An issue where WebExtensions can use the mozAddonManager API to elevate privilege due to privileged pages being allowed in the permissions list. This allows a malicious extension to then install additional extensions without explicit user permission. This vulnerability affects Firefox < 50.
https://www.mozilla.org/security/advisories/mfsa2016-89/
https://bugzilla.mozilla.org/show_bug.cgi?id=1295324