A Firefox security update has been released for Ubuntu Linux 16.04 LTS, 18.04 LTS, 20.04 LTS, and 20.10.

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Ubuntu Security Notice USN-4717-1
February 01, 2021

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
- Ubuntu 16.04 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, conduct clickjacking 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 85.0+build1-0ubuntu0.20.10.1

Ubuntu 20.04 LTS:
firefox 85.0+build1-0ubuntu0.20.04.1

Ubuntu 18.04 LTS:
firefox 85.0+build1-0ubuntu0.18.04.1

Ubuntu 16.04 LTS:
firefox 85.0+build1-0ubuntu0.16.04.1

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

References:
  https://usn.ubuntu.com/4717-1
CVE-2021-23953, CVE-2021-23954, CVE-2021-23955, CVE-2021-23956,
CVE-2021-23958, CVE-2021-23960, CVE-2021-23961, CVE-2021-23962,
CVE-2021-23963, CVE-2021-23964, CVE-2021-23965

Package Information:
  https://launchpad.net/ubuntu/+source/firefox/85.0+build1-0ubuntu0.20.10.1
  https://launchpad.net/ubuntu/+source/firefox/85.0+build1-0ubuntu0.20.04.1
  https://launchpad.net/ubuntu/+source/firefox/85.0+build1-0ubuntu0.18.04.1
  https://launchpad.net/ubuntu/+source/firefox/85.0+build1-0ubuntu0.16.04.1