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Fencer Intel
medium 6.1

CVE-2020-15676 json

Firefox sometimes ran the onload handler for SVG elements that the DOM sanitizer decided to remove, resulting in JavaScript being executed…

published 6y ago modified 4mo ago also EUVD-2020-7663

cvss
6.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.6%
EPSS 1.6% chance of exploitation in 30 days, percentile 75%
public exploits
0
none known

Summary

Firefox sometimes ran the onload handler for SVG elements that the DOM sanitizer decided to remove, resulting in JavaScript being executed after pasting attacker-controlled data into a contenteditable element. This vulnerability affects Firefox < 81, Thunderbird < 78.3, and Firefox ESR < 78.3.

Patch / fix

  • Mozilla Firefox 81
  • Mozilla Thunderbird 78.3
  • Mozilla Firefox ESR 78.3
  • firefox-esr Debian 14, Debian 13, Debian 12 78.3.0esr-1
  • thunderbird Debian 14, Debian 13, Debian 12 1:78.3.1-1

debian advisories DEBIAN-CVE-2020-15676

  • firefox Ubuntu 16.04 LTS 81.0+build2-0ubuntu0.16.04.1
  • firefox Ubuntu 18.04 LTS 81.0+build2-0ubuntu0.18.04.1
  • firefox Ubuntu 20.04 LTS 81.0+build2-0ubuntu0.20.04.1
  • thunderbird Ubuntu 18.04 LTS 1:78.8.1+build1-0ubuntu0.18.04.1
  • thunderbird Ubuntu 20.04 LTS 1:78.7.1+build1-0ubuntu0.20.04.1

ubuntu advisories UBUNTU-CVE-2020-15676

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • thunderbird RHEL 6 78.3.1-1.el6_10
  • thunderbird RHEL 7 78.3.1-1.el7_9
  • thunderbird RHEL 8 78.3.1-1.el8_2
  • firefox RHEL 7 78.3.0-1.el7_9
  • firefox RHEL 8 78.3.0-1.el8_2
  • firefox RHEL 6 78.3.0-1.el6_10
  • thunderbird RHEL 8.1 EUS 78.3.1-1.el8_1
  • thunderbird RHEL 8.0 E4S 78.3.1-1.el8_0

red hat advisories RHSA-2020:4157RHSA-2020:4156RHSA-2020:4158RHSA-2020:4163RHSA-2020:4155RHSA-2020:4080

  • mozilla-nspr SLE Module for Basesystem 15 SP2, SLE Module for Basesystem 15 SP1 4.25.1-3.15.2
  • MozillaThunderbird SLE Workstation Extension 15 SP2, SLE Workstation Extension 15 SP1 78.4.0-3.99.1
  • MozillaFirefox SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +15 more 78.3.0-112.22.1
  • MozillaFirefox SLE Module for Desktop Applications 15 SP2 78.3.0-8.6.1
  • MozillaFirefox SLE Module for Desktop Applications 15 SP1 78.3.0-3.108.1
  • MozillaFirefox SLES 11 SP4-LTSS 78.3.0-78.93.1

suse advisories SUSE-SU-2020:3091-1SUSE-SU-2020:14502-1SUSE-SU-2020:2759-1SUSE-SU-2020:2749-1SUSE-SU-2020:2747-1

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 92.0-1.2
  • MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1
  • mozilla-nspr openSUSE Leap 15.1 4.25.1-lp151.2.13.1
  • MozillaThunderbird openSUSE Leap 15.1 78.4.0-lp151.2.53.1
  • mozilla-nspr openSUSE Leap 15.2 4.25.1-lp152.2.3.1
  • MozillaThunderbird openSUSE Leap 15.2 78.4.0-lp152.2.13.1
  • MozillaFirefox openSUSE Leap 15.2 78.3.0-lp152.2.21.1

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:10600-1openSUSE-SU-2024:10601-1openSUSE-SU-2020:1785-1openSUSE-SU-2020:1780-1openSUSE-SU-2020:1574-1

  • firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 81.0-r0
  • librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 81.0-r0
  • firefox-esr Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 78.3.0-r0

alpine advisories ALPINE-CVE-2020-15676

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • firefox Arch Linux 81.0-1

arch linux advisories AVG-1235

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-15676 updated cvss 6.1

Mozilla: XSS when pasting attacker-controlled data into a contenteditable element

  • Red Hat Enterprise Linux 5 firefox, thunderbird
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) firefox 78.3.0-1.el8_2, thunderbird 78.3.1-1.el8_2
    fixed: vendor fix RHSA-2020:3832
  • Red Hat Enterprise Linux AppStream E4S (v. 8.0) firefox 78.3.0-1.el8_0, thunderbird 78.3.1-1.el8_0
    fixed: vendor fix RHSA-2020:3834
  • Red Hat Enterprise Linux AppStream EUS (v. 8.1) firefox 78.3.0-1.el8_1, thunderbird 78.3.1-1.el8_1
    fixed: vendor fix RHSA-2020:3833
  • Red Hat Enterprise Linux Client (v. 7) firefox 78.3.0-1.el7_9, thunderbird 78.3.1-1.el7_9 Red Hat Enterprise Linux Client Optional (v. 7) firefox 78.3.0-1.el7_9
    fixed: vendor fix RHSA-2020:4080
  • Red Hat Enterprise Linux Desktop (v. 6) firefox 78.3.0-1.el6_10, thunderbird 78.3.1-1.el6_10 Red Hat Enterprise Linux Desktop Optional (v. 6) firefox 78.3.0-1.el6_10 Red Hat Enterprise Linux HPC Node Optional (v. 6) firefox 78.3.0-1.el6_10 Red Hat Enterprise Linux Server (v. 6) firefox 78.3.0-1.el6_10
    fixed: vendor fix RHSA-2020:3835
  • Red Hat Enterprise Linux Server (v. 7) firefox 78.3.0-1.el7_9
    fixed: vendor fix RHSA-2020:4080
  • Red Hat Enterprise Linux Server Optional (v. 6) firefox 78.3.0-1.el6_10, thunderbird 78.3.1-1.el6_10
    fixed: vendor fix RHSA-2020:3835
show 5 more
  • Red Hat Enterprise Linux Server Optional (v. 7) firefox 78.3.0-1.el7_9, thunderbird 78.3.1-1.el7_9
    fixed: vendor fix RHSA-2020:4080
  • Red Hat Enterprise Linux Workstation (v. 6) firefox 78.3.0-1.el6_10, thunderbird 78.3.1-1.el6_10
    fixed: vendor fix RHSA-2020:3835
  • Red Hat Enterprise Linux Workstation (v. 7) firefox 78.3.0-1.el7_9, thunderbird 78.3.1-1.el7_9
    fixed: vendor fix RHSA-2020:4080
  • Red Hat Enterprise Linux Workstation Optional (v. 6) firefox 78.3.0-1.el6_10
    fixed: vendor fix RHSA-2020:3835
  • Red Hat Enterprise Linux Workstation Optional (v. 7) firefox 78.3.0-1.el7_9
    fixed: vendor fix RHSA-2020:4080

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.59% chance of exploitation in the next 30 days, higher than 75% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N

Affected products

  • Mozilla Firefox
  • Mozilla Thunderbird
  • Mozilla Firefox ESR

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.