Cross-site Scripting in Sanitize

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

EPSS

• CVE-2020-4054: 1.92% estimated exploitation activity in the next 30 days; percentile 79.90 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

When HTML is sanitized using Sanitize's "relaxed" config or a custom config that allows certain elements, some content in a <math or <svg element may not be sanitized correctly even if math and svg are not in the allowlist. You are likely to be vulnerable to this issue if you use Sanitize's relaxed config or a custom config that allows one or more of the following HTML elements: - iframe - math - noembed - noframes - noscript - plaintext - script - style - svg - xmp Impact Using carefully crafted input, an attacker may be able to sneak arbitrary HTML through Sanitize, potentially resulting in XSS (cross-site scripting) or other undesired behavior when that HTML is rendered in a browser. Releases This problem has been fixed in Sanitize 5.2.1. Workarounds If upgrading is not possible, a workaround is to override the default value of Sanitize's :removecontents config option with the following value, which ensures that the contents of math and svg elements (among others) are removed…

Published by the source

16 Jun 2020, 22:08 UTC

Last modified by the source

16 May 2023, 16:18 UTC

Source last checked

26 Oct 2026, 15:47 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-p4x4-rw2p-8j8m

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# Patch Next advisory brief: CVE-2020-4054

Advisory: Cross-site Scripting in Sanitize
IDs: CVE-2020-4054, GHSA-p4x4-rw2p-8j8m
Record: https://patchnext.com/advisories/cve-2020-4054 (revision 1, source checked 26 Oct 2026, 15:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: sanitize 5.2.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems sanitize: affected >= 3.0.0, < 5.2.1; fixed in 5.2.1

## Suggested inspection (read-only)
- RubyGems sanitize: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on sanitize.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-p4x4-rw2p-8j8m (GitHub-reviewed advisory GHSA-p4x4-rw2p-8j8m lists affected ranges: RubyGems sanitize >=3.0.0 <5.2.1)

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