Cross-site Scripting in SEOmatic plugin

Exploitation

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

CVSS

6.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2021-41750: 1.13% estimated exploitation activity in the next 30 days; percentile 66.36 (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.

A cross-site scripting (XSS) vulnerability in the SEOmatic plugin 3.4.10 for Craft CMS 3 allows remote attackers to inject arbitrary web script via a GET to /index.php?action=seomatic/file/seo-file-link with url parameter containing the base64 encoded URL of a malicious web page / file and fileName parameter containing an arbitrary filename with the intended content-type to be rendered in the user's browser as the extension.

Published by the source

13 Jun 2022, 00:00 UTC

Last modified by the source

27 Jan 2023, 05:03 UTC

Source last checked

26 Oct 2026, 13:59 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-6hjc-m38h-7jhh

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# Patch Next advisory brief: CVE-2021-41750

Advisory: Cross-site Scripting in SEOmatic plugin
IDs: CVE-2021-41750, GHSA-6hjc-m38h-7jhh
Record: https://patchnext.com/advisories/cve-2021-41750 (revision 1, source checked 26 Oct 2026, 13:59 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: nystudio107/craft-seomatic 3.4.11. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist nystudio107/craft-seomatic: affected < 3.4.11; fixed in 3.4.11

## Suggested inspection (read-only)
- Packagist nystudio107/craft-seomatic: 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 nystudio107/craft-seomatic.
- 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-6hjc-m38h-7jhh (GitHub-reviewed advisory GHSA-6hjc-m38h-7jhh lists affected ranges: Packagist nystudio107/craft-seomatic >=0 <3.4.11)

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