USN-2936-3: Firefox regression

USN-2936-1 fixed vulnerabilities in Firefox. The update caused an issue
where a device update POST request was sent every time about:preferences#sync
was shown. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

Christian Holler, Tyson Smith, Phil Ringalda, Gary Kwong, Jesse Ruderman,
Mats Palmgren, Carsten Book, Boris Zbarsky, David Bolter, Randell Jesup,
Andrew McCreight, and Steve Fink discovered multiple memory safety issues
in Firefox. If a user were tricked in to opening a specially crafted
website, an attacker could potentially exploit these to cause a denial of
service via application crash, or execute arbitrary code with the
privileges of the user invoking Firefox. (CVE-2016-2804, CVE-2016-2806,
CVE-2016-2807)

An invalid write was discovered when using the JavaScript .watch() method in
some circumstances. If a user were tricked in to opening a specially crafted
website, an attacker could potentially exploit this to cause a denial of
service via application crash, or execute arbitrary code with the
privileges of the user invoking Firefox. (CVE-2016-2808)

Looben Yang discovered a use-after-free and buffer overflow in service
workers. If a user were tricked in to opening a specially crafted website,
an attacker could potentially exploit these to cause a denial of service
via application crash, or execute arbitrary code with the privileges of
the user invoking Firefox. (CVE-2016-2811, CVE-2016-2812)

Sascha Just discovered a buffer overflow in libstagefright in some
circumstances. If a user were tricked in to opening a specially crafted
website, an attacker could potentially exploit this to cause a denial of
service via application crash, or execute arbitrary code with the
privileges of the user invoking Firefox. (CVE-2016-2814)

Muneaki Nishimura discovered that CSP is not applied correctly to web
content sent with the multipart/x-mixed-replace MIME type. An attacker
could potentially exploit this to conduct cross-site scripting (XSS)
attacks when they would otherwise be prevented. (CVE-2016-2816)

Muneaki Nishimura discovered that the chrome.tabs.update API for web
extensions allows for navigation to javascript: URLs. A malicious
extension could potentially exploit this to conduct cross-site scripting
(XSS) attacks. (CVE-2016-2817)

Mark Goodwin discovered that about:healthreport accepts certain events
from any content present in the remote-report iframe. If another
vulnerability allowed the injection of web content in the remote-report
iframe, an attacker could potentially exploit this to change the user's
sharing preferences. (CVE-2016-2820)