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.
- 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
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.
Which versions are affected by CVE-2026-91127?
4 open source packages ship an affected version, including @file-viewer/doc and msdoc-viewer.
| Package | 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.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-91127 being exploited?
There is no known exploitation of CVE-2026-91127 in the wild and no public exploit code.
Sources
Also known as GHSA-3753-m2x2-q623.