Sveltia CMS: Stored XSS in entry summary rendering via entity-decoded HTML

Exploitation

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

CVSS 4.0

2.3 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Impact A stored cross-site scripting (XSS) vulnerability affected entry summary rendering in Sveltia CMS. Entry summaries that allowed limited Markdown were parsed, sanitized, and then HTML entities were decoded. This order allowed specially crafted entity-encoded HTML, such as encoded tags or event handler attributes, to become active HTML after sanitization. When the resulting summary was rendered in the CMS UI, arbitrary JavaScript could execute in the browser of a user viewing the affected entry list or search result. The practical impact is limited in currently supported Sveltia CMS usage because the CMS is intended for a single developer or a small trusted team, and open authoring / untrusted multi-user authoring is not currently implemented. Exploitation requires the ability to place malicious content into the repository or content source that the CMS loads.

Patches The issue has been patched by changing entry summary…

Published by the source

18 May 2026, 13:43 UTC

Last modified by the source

18 May 2026, 14:02 UTC

Source last checked

24 Oct 2026, 22:39 UTC

1. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-97r8-rf7q-wmjw

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# Patch Next advisory brief: GHSA-97r8-rf7q-wmjw

Advisory: Sveltia CMS: Stored XSS in entry summary rendering via entity-decoded HTML
IDs: GHSA-97r8-rf7q-wmjw
Record: https://patchnext.com/advisories/ghsa-97r8-rf7q-wmjw (revision 2, source checked 24 Oct 2026, 22:39 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @sveltia/cms 0.160.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @sveltia/cms: affected < 0.160.1; fixed in 0.160.1

## Suggested inspection (read-only)
- `npm ls @sveltia/cms --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## 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 @sveltia/cms.
- 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://osv.dev/vulnerability/GHSA-97r8-rf7q-wmjw (OSV record GHSA-97r8-rf7q-wmjw lists affected ranges: npm @sveltia/cms >=0 <0.160.1 (fixed))

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