Updated firefox packages has been released for Ubuntu 14.04 LTS, 16.04 LTS, and 17.04 to address a regression

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Ubuntu Security Notice USN-3435-2
October 04, 2017

firefox regression
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 17.04
- Ubuntu 16.04 LTS
- Ubuntu 14.04 LTS

Summary:

USN-3435-1 caused a regression in Firefox.

Software Description:
- firefox: Mozilla Open Source web browser

Details:

USN-3435-1 fixed vulnerabilities in Firefox. The update caused the Flash
plugin to crash in some circumstances. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

Multiple security issues were discovered in Firefox. If a user were
tricked in to opening a specially crafted website, an attacker could
potentially exploit these to read uninitialized memory, obtain sensitive
information, bypass phishing and malware protection, spoof the origin in
modal dialogs, conduct cross-site scripting (XSS) attacks, cause a denial
of service via application crash, or execute arbitrary code.
(CVE-2017-7793, CVE-2017-7810, CVE-2017-7811, CVE-2017-7812,
CVE-2017-7813, CVE-2017-7814, CVE-2017-7815, CVE-2017-7818, CVE-2017-7819,
CVE-2017-7820, CVE-2017-7822, CVE-2017-7823, CVE-2017-7824)

Martin Thomson discovered that NSS incorrectly generated handshake hashes.
A remote attacker could potentially exploit this to cause a denial of
service via application crash, or execute arbitrary code. (CVE-2017-7805)

Multiple security issues were discovered in WebExtensions. If a user were
tricked in to installing a specially crafted extension, an attacker could
potentially exploit these to download and open non-executable files
without interaction, or obtain elevated privileges. (CVE-2017-7816,
CVE-2017-7821)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 17.04:
firefox 56.0+build6-0ubuntu0.17.04.2

Ubuntu 16.04 LTS:
firefox 56.0+build6-0ubuntu0.16.04.2

Ubuntu 14.04 LTS:
firefox 56.0+build6-0ubuntu0.14.04.2

After a standard system update you need to restart Firefox to make
all the necessary changes.

References:
https://www.ubuntu.com/usn/usn-3435-2
https://www.ubuntu.com/usn/usn-3435-1
https://launchpad.net/bugs/1720908

Package Information:
https://launchpad.net/ubuntu/+source/firefox/56.0+build6-0ubuntu0.17.04.2
https://launchpad.net/ubuntu/+source/firefox/56.0+build6-0ubuntu0.16.04.2
https://launchpad.net/ubuntu/+source/firefox/56.0+build6-0ubuntu0.14.04.2

  Firefox Regression Fix Update for Ubuntu