Changes

* Related bugs:** https://bugzilla.mozilla.org/show_bug.cgi?id=783638** https://bugzilla.mozilla.org/show_bug.cgi?id=715816** https://bugzilla.mozilla.org/show_bug.cgi?id=792452 === Risks ===* Compromised update package data, resulting in an untrusted update package being installed* Compromised update check, user does not see new updates are available* System state compromised or unknown during the installation of the update* Vulnerabilities in the update checking mechanism* Lack of updates or tracking for a software component with a known vulnerability === Implementation === * See the Security Review for the implementation information** https://wiki.mozilla.org/Security/Reviews/B2GUpdates === Proposed Additional Implementation: Tracking of applications versions for known security patches ===