USN-4671-1: Firefox vulnerabilities

15 December 2020

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



  • firefox - Mozilla Open Source web browser


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, bypass the CSS sanitizer, bypass security restrictions,
spoof the URL bar, or execute arbitrary code. (CVE-2020-16042,
CVE-2020-26971, CVE-2020-26972, CVE-2020-26793, CVE-2020-26974,
CVE-2020-26976, CVE-2020-26978, CVE-2020-26979,
CVE-2020-35113, CVE-2020-35114)

It was discovered that the proxy.onRequest API did not catch
view-source URLs. If a user were tricked in to installing an
extension with the proxy permission and opening View Source, an
attacker could potentially exploit this to obtain sensitive
information. (CVE-2020-35111)

Update instructions

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

Ubuntu 20.10
Ubuntu 20.04
Ubuntu 18.04
Ubuntu 16.04

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

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