HTML tags received from the Pocket server will be processed without sanitization and any JavaScript code executed will be run in the "about:pocket-saved" (unprivileged) page, giving it access to Pocket's messaging API through HTML injection. This vulnerability affects Firefox ESR < 45.6 and Firefox < 50.1.
https://www.mozilla.org/security/advisories/mfsa2016-95/
https://www.mozilla.org/security/advisories/mfsa2016-94/
https://security.gentoo.org/glsa/201701-15
https://bugzilla.mozilla.org/show_bug.cgi?id=1320057
http://www.securitytracker.com/id/1037461
http://www.securityfocus.com/bid/94885