A Firefox security update has been released for Ubuntu 18.04 LTS, 20.04 LTS, and 20.10.

USN-4637-1: Firefox vulnerabilities

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Ubuntu Security Notice USN-4637-1
November 18, 2020

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

- Ubuntu 20.10
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

Firefox could be made to crash or run programs as your login if it
opened a malicious website.

Software Description:
- firefox: Mozilla Open Source web browser

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 cause a denial of service, obtain sensitive
information across origins, bypass security restrictions, conduct phishing
attacks, conduct cross-site scripting (XSS) attacks, bypass Content
Security Policy (CSP) restrictions, conduct DNS rebinding attacks, or
execute arbitrary code.

Update instructions:

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

Ubuntu 20.10:
firefox 83.0+build2-0ubuntu0.20.10.1

Ubuntu 20.04 LTS:
firefox 83.0+build2-0ubuntu0.20.04.1

Ubuntu 18.04 LTS:
firefox 83.0+build2-0ubuntu0.18.04.2

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

References:
  https://usn.ubuntu.com/4637-1
CVE-2020-16012, CVE-2020-26951, CVE-2020-26952, CVE-2020-26953,
CVE-2020-26956, CVE-2020-26958, CVE-2020-26959, CVE-2020-26960,
CVE-2020-26961, CVE-2020-26962, CVE-2020-26963, CVE-2020-26965,
CVE-2020-26967, CVE-2020-26968, CVE-2020-26969

Package Information:
  https://launchpad.net/ubuntu/+source/firefox/83.0+build2-0ubuntu0.20.10.1
  https://launchpad.net/ubuntu/+source/firefox/83.0+build2-0ubuntu0.20.04.1
  https://launchpad.net/ubuntu/+source/firefox/83.0+build2-0ubuntu0.18.04.2