# CVE-2026-91127: File Viewer: DOM XSS via unsafe hyperlink schemes in the legacy DOC renderer

> Attackers can execute arbitrary JavaScript in the embedding application's origin by tricking users into clicking malicious links in crafted DOC files.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 18 Sep 2026
- **Updated:** 22 Sep 2026
- **Also known as:** GHSA-3753-m2x2-q623

## What is CVE-2026-91127?

CVE-2026-91127 is a high-severity cross-site scripting vulnerability in @file-viewer doc, published on 18 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-83 (Improper Neutralization of Script in Attributes in a Web Page), CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-91127?

4 open source packages ship an affected version, including @file-viewer/doc and msdoc-viewer.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@file-viewer/doc` | npm | All versions | 2.3.1 |
| `@file-viewer/doc` | npm | All versions | 2.3.1 |
| `msdoc-viewer` | npm | All versions | 0.2.2 |
| `msdoc-viewer` | npm | All versions | 0.2.2 |

## How do I fix CVE-2026-91127?

Upgrade @file-viewer/doc to 2.3.1 or later.

## Is CVE-2026-91127 being exploited?

There is no known exploitation of CVE-2026-91127 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-91127 and fix it if it is affected.

What it is: CVE-2026-91127 is a high-severity cross-site scripting vulnerability in @file-viewer doc, published on 18 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-91127 in the wild and no public exploit code.

Affected packages and fixed versions:
- @file-viewer/doc (npm): affected all versions; fixed in 2.3.1
- @file-viewer/doc (npm): affected all versions; fixed in 2.3.1
- msdoc-viewer (npm): affected all versions; fixed in 0.2.2
- msdoc-viewer (npm): affected all versions; fixed in 0.2.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-91127/ (Markdown: https://insights.sbomify.com/CVE-2026-91127/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-91127
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-91127
- OSV: https://osv.dev/vulnerability/CVE-2026-91127

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-91127/
Summaries are generated and may contain mistakes; the official description above is the record.