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High, CVSS 8.2amended

File Viewer: DOM XSS via unsafe hyperlink schemes in the legacy DOC renderer

CVE-2026-91127GHSA-3753-m2x2-q623

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (msdoc-viewer 0.2.2; @file-viewer/doc 2.3.1), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.2 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N
EPSS
  • CVE-2026-91127: 0.40% estimated exploitation activity in the next 30 days; percentile 33.92 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary Before 2.3.1, the legacy .doc renderer emitted document hyperlink targets after HTML escaping but without a URL-scheme allowlist. A crafted .doc could therefore render a live javascript:, vbscript:, data:, or similarly unsafe link. Script could execute in the embedding origin if a viewer clicked it. Impact Applications rendering untrusted legacy .doc files with @file-viewer/doc or the msdoc-viewer compatibility package could expose their origin to attacker-controlled script after link interaction. Fix Version 2.3.1 centralizes link handling, removes control-character and scheme confusion, blocks external document links by default, and in explicit allow mode accepts only HTTP(S), mail, telephone, safe relative URLs, and internal bookmarks. The renderer output is safe before mounting, with mount-boundary sanitization as defense in depth. The msdoc-viewer compatibility release containing the fix is 0.2.2. Thanks to @shashank420 for responsibly reporting this issue.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-3753-m2x2-q623

  2. Revision 2 · amended ·

    Amended from osv record GHSA-3753-m2x2-q623

  3. Revision 1 · created ·

    Published from ghsa record GHSA-3753-m2x2-q623

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-91127

Advisory: File Viewer: DOM XSS via unsafe hyperlink schemes in the legacy DOC renderer
IDs: CVE-2026-91127, GHSA-3753-m2x2-q623
Record: https://patchnext.com/advisories/cve-2026-91127 (revision 3, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: msdoc-viewer 0.2.2; @file-viewer/doc 2.3.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm msdoc-viewer: affected <= 0.2.1; fixed in 0.2.2
- npm @file-viewer/doc: affected <= 2.3.0; fixed in 2.3.1

## Suggested inspection (read-only)
- `npm ls msdoc-viewer --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @file-viewer/doc --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 msdoc-viewer, @file-viewer/doc.
- 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-3753-m2x2-q623 (GitHub-reviewed advisory GHSA-3753-m2x2-q623 lists affected ranges: npm @file-viewer/doc >=0 =0 <=0.2.1)
- Verified: https://osv.dev/vulnerability/GHSA-3753-m2x2-q623 (OSV record GHSA-3753-m2x2-q623 lists affected ranges: npm @file-viewer/doc >=0 =0 <0.2.2 (fixed))

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