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CVE-2026-91127 high CVSS 8.2

Cross-Site Scripting (XSS) in @file-viewer/doc (CVE-2026-91127)

Summary

Cross-site scripting in @file-viewer/doc (CVE-2026-91127). Confidential information can be exposed externally. Mitigation: upgrade to 2.3.1 or later.

Original description

The description as published by the source.

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.

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-91127 has been found in @file-viewer/doc.
Confidential information can be exposed externally. CVSS score: 8.2/10.
What to do: upgrade @file-viewer/doc to 2.3.1 or later.
If unsure, ask your IT team or search "@file-viewer/doc CVE-2026-91127" on the vendor's site.

CVE-2026-91127 (@file-viewer/doc) — CWE-79 / CVSS v3 8.2
Attack vector: remote (network-reachable) / unauthenticated
Patched: 2.3.1 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Cross-site scripting (XSS) (CWE-79) exists in @file-viewer/doc.

📍 Affected scope

Check the vendor advisory for the affected versions of @file-viewer/doc.

🔥 Severity

Severity: High (CVSS 8.2/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 2.3.1.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r '@file-viewer/doc' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r '@file-viewer/doc' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で @file-viewer/doc を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade @file-viewer/doc to 2.3.1

    ステージング環境で 2.3.1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

npm @file-viewer/doc
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.3.1"}]}]
npm msdoc-viewer
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.2.2"}]}]

References

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