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-4893-1
March 25, 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 into opening a specially crafted website, an attacker could
potentially exploit these to cause a denial of service, obtain sensitive
information, or execute arbitrary code. (CVE-2021-23981, CVE-2021-23982,
CVE-2021-23983, CVE-2021-23987, CVE-2021-23988)

It was discovered that extensions could open popup windows with control
of the window title in some circumstances. If a user were tricked into
installing a specially crafted extension, an attacker could potentially
exploit this to spook a website and trick the user into providing
credentials. (CVE-2021-23984)

It was discovered that the DevTools remote debugging feature could be
enabled without an indication to the user. If a local attacker could
modify the browser configuration, a remote attacker could potentially
exploit this to obtain sensitive information. (CVE-2021-23985)

It was discovered that extensions could read the response of cross
origin requests in some circumstances. If a user were tricked into
installing a specially crafted extension, an attacker could potentially
exploit this to obtain sensitive information. (CVE-2021-23986)

Update instructions:

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

Ubuntu 20.10:
firefox 87.0+build3-0ubuntu0.20.10.1

Ubuntu 20.04 LTS:
firefox 87.0+build3-0ubuntu0.20.04.2

Ubuntu 18.04 LTS:
firefox 87.0+build3-0ubuntu0.18.04.2

Ubuntu 16.04 LTS:
firefox 87.0+build3-0ubuntu0.16.04.2

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

References:
  https://ubuntu.com/security/notices/USN-4893-1
CVE-2021-23981, CVE-2021-23982, CVE-2021-23983, CVE-2021-23984,
CVE-2021-23985, CVE-2021-23986, CVE-2021-23987, CVE-2021-23988

Package Information:
  https://launchpad.net/ubuntu/+source/firefox/87.0+build3-0ubuntu0.20.10.1
  https://launchpad.net/ubuntu/+source/firefox/87.0+build3-0ubuntu0.20.04.2
  https://launchpad.net/ubuntu/+source/firefox/87.0+build3-0ubuntu0.18.04.2
  https://launchpad.net/ubuntu/+source/firefox/87.0+build3-0ubuntu0.16.04.2