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.
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00074.html
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00077.html
https://bugzilla.mozilla.org/show_bug.cgi?id=1646140
https://lists.debian.org/debian-lts-announce/2020/10/msg00020.html
https://security.gentoo.org/glsa/202010-02
https://www.debian.org/security/2020/dsa-4770
https://www.mozilla.org/security/advisories/mfsa2020-42/
Source: MITRE
Published: 2020-10-01
Updated: 2020-11-02
Type: CWE-79
Base Score: 4.3
Vector: AV:N/AC:M/Au:N/C:N/I:P/A:N
Impact Score: 2.9
Exploitability Score: 8.6
Severity: MEDIUM
Base Score: 6.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Impact Score: 2.7
Exploitability Score: 2.8
Severity: MEDIUM