Description
File Viewer is a browser-native viewer for Office, PDF, CAD, archive, and other files in private and internal web applications. Prior to @file-viewer/doc 2.3.1 and msdoc-viewer 0.2.2, the legacy DOC renderer emitted document-controlled hyperlink targets into generated HTML after character escaping but without restricting URL schemes. A crafted legacy DOC file could place javascript:, vbscript:, data:, or another unsafe scheme in a rendered link, and script could execute in the embedding application's origin when a user clicked the link. The fix blocks external document links by default, allows only HTTP(S), mail, telephone, safe relative URLs, and internal bookmarks when external links are explicitly enabled, and applies mount-boundary sanitization as defense in depth. This issue is fixed in @file-viewer/doc 2.3.1 and msdoc-viewer 0.2.2.
Published: 2026-09-18
Score: 8.2 High
EPSS: < 1% Very Low
KEV: No
Impact: DOM Cross‑Site Scripting that can execute arbitrary JavaScript within the embedding web application’s origin
Action: Patch Immediately
AI Analysis

Impact

The legacy DOC renderer in File Viewer emits hyperlink targets into the generated HTML after escaping content, but does not restrict the URL scheme. A maliciously crafted legacy DOC file can include schemes such as javascript:, vbscript:, data:, or other unsafe schemes in a link. When a user clicks that link, the script runs in the context of the host web application, allowing arbitrary JavaScript execution within the embedding application's origin.

Affected Systems

Affected vendors include @file-viewer and flyfish‑dev with the products @file-viewer/doc, flyfish‑dev:file‑viewer, and flyfish‑dev:msdoc‑viewer. All versions prior to @file-viewer/doc 2.3.1 and msdoc‑viewer 0.2.2 are vulnerable. Updates as indicated in the referenced releases and security advisory resolve the issue.

Risk and Exploitability

The CVSS score of 8.2 indicates high severity. The EPSS score is below 1 %, indicating a low probability of exploitation in the wild at present. The issue is not listed in the CISA KEV catalog. The likely attack vector involves an application that loads legacy DOC files; a crafted document can be supplied by an attacker, and the victim must click an unsafe link for the script to run. Once executed, the attacker can run arbitrary JavaScript within the hosting web application’s client side.

Generated by OpenCVE AI on September 19, 2026 at 16:43 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade @file‑viewer/doc to version 2.3.1 or later and flyfish‑dev:msdoc‑viewer to 0.2.2 (or newer) to apply the vendor‑provided fix.
  • If the upgrade cannot be performed immediately, disable the legacy DOC renderer or configure the application to reject external hyperlink schemes; only allow HTTP(S), mailto, tel, safe relative URLs, and internal bookmarks.
  • Apply additional client‑side sanitization or enforce a Content Security Policy that blocks javascript:, vbscript:, data: schemes and limits script execution to trusted sources.

Generated by OpenCVE AI on September 19, 2026 at 16:43 UTC.

Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-3753-m2x2-q623 File Viewer: DOM XSS via unsafe hyperlink schemes in the legacy DOC renderer
History

Wed, 23 Sep 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Sat, 19 Sep 2026 23:00:00 +0000

Type Values Removed Values Added
First Time appeared Flyfish-dev
Flyfish-dev file-viewer
Flyfish-dev msdoc-viewer
Vendors & Products Flyfish-dev
Flyfish-dev file-viewer
Flyfish-dev msdoc-viewer

Fri, 18 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
Description File Viewer is a browser-native viewer for Office, PDF, CAD, archive, and other files in private and internal web applications. Prior to @file-viewer/doc 2.3.1 and msdoc-viewer 0.2.2, the legacy DOC renderer emitted document-controlled hyperlink targets into generated HTML after character escaping but without restricting URL schemes. A crafted legacy DOC file could place javascript:, vbscript:, data:, or another unsafe scheme in a rendered link, and script could execute in the embedding application's origin when a user clicked the link. The fix blocks external document links by default, allows only HTTP(S), mail, telephone, safe relative URLs, and internal bookmarks when external links are explicitly enabled, and applies mount-boundary sanitization as defense in depth. This issue is fixed in @file-viewer/doc 2.3.1 and msdoc-viewer 0.2.2.
Title File Viewer: DOM XSS via unsafe hyperlink schemes in the legacy DOC renderer
Weaknesses CWE-79
CWE-83
References
Metrics cvssV3_1

{'score': 8.2, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N'}

Subscriptions

Flyfish-dev File-viewer Msdoc-viewer
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-22T15:10:24.440Z

Reserved: 2026-09-14T19:36:48.844Z

Link: CVE-2026-91127

cve-icon Vulnrichment

Updated: 2026-09-22T15:10:19.589Z

cve-icon NVD

Status : Deferred

Published: 2026-09-18T18:18:02.250

Modified: 2026-09-24T21:25:27.050

Link: CVE-2026-91127

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-19T22:28:36Z

Weaknesses
  • CWE-79

    Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

  • CWE-83

    Improper Neutralization of Script in Attributes in a Web Page