These release notes are incomplete.
The Mozilla JavaScript team is pleased to announce the release of SpiderMonkey 52. You can download full source code from treeherder, by going to the mozilla-esr52 repository and clicking on the first SM(pkg) link you see. That will open a small window in the bottom left with a line like "artifact uploaded:mozjs-52.x.y.tar.bz2".
SpiderMonkey 52 is the JavaScript engine that shipped in Firefox 52. It continues to improve performance over previous SpiderMonkey releases. It also contains new language and API features described in detail below.
Please let us know about your experiences with this release by posting in the mozilla.dev.tech.js-engine newsgroup. Or file bugs at bugzilla.mozilla.org under Product: Core, Component: JavaScript engine. You may wish to make the bugs block bug 837921 (aliased as "sm.embedding").