CVE-2026-91127

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

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.

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.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2026-91127 has a CVSS score of 8.2 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.3.1, 0.2.2); upgrading removes the vulnerable code path.

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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.

1. What is CVE-2026-91127? CVE-2026-91127 is a high-severity cross-site scripting (XSS) vulnerability in @file-viewer/doc (npm), affecting versions <= 2.3.0. It is fixed in 2.3.1, 0.2.2. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2026-91127? CVE-2026-91127 has a CVSS score of 8.2 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2026-91127?
   • @file-viewer/doc (npm) (versions <= 2.3.0)
   • msdoc-viewer (npm) (versions <= 0.2.1)
4. Is there a fix for CVE-2026-91127? Yes. CVE-2026-91127 is fixed in 2.3.1, 0.2.2. Upgrade to this version or later.
5. Is CVE-2026-91127 exploitable, and should I be worried? Whether CVE-2026-91127 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-91127 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-91127?
   • Upgrade @file-viewer/doc to 2.3.1 or later
   • Upgrade msdoc-viewer to 0.2.2 or later