Emissary is a P2P based data-driven workflow engine. Prior to 8.39.0, Mustache navigation templates interpolated configuration-controlled link values directly into href attributes without URL scheme validation. An administrator who could modify the navItems configuration could inject javascript: URIs, enabling stored cross-site scripting (XSS) against other authenticated users viewing the Emissary web interface. This vulnerability is fixed in 8.39.0.

Affected: Maven: gov.nsa.emissary:emissary

## Summary

Mustache navigation templates interpolated configuration-controlled link values directly into `href` attributes without URL scheme validation. An administrator who could modify the `navItems` configuration could inject `javascript:` URIs, enabling stored cross-site scripting (XSS) against other authenticated users viewing the Emissary web interface.

## Details

### Vulnerable code — `nav.mustache` (line 10)

```html {{#navItems}} <li class="nav-item"> <a class="nav-link" href="{{link}}">{{display}}</a> </li> {{/navItems}} ```

The `{{link}}` value was rendered without any scheme validation. Mustache's default HTML escaping protects against injection of new HTML tags but does **not** prevent `javascript:` URIs in `href` attributes, since `javascript:` contains no characters that HTML-escaping would alter.

### Attack vector

An administrator sets a navigation item's link to: ``` javascript:alert(document.cookie) ```

Any authenticated user who clicks the navigation link executes the script in their browser context.

### Impact

- Session hijacking via cookie theft - Actions performed on behalf of the victim user - Requires administrative access to modify navigation configuration - Requires user interaction (clicking the malicious link)

### Mitigating factors

- Exploitation requires administrative access to modify the `navItems` configuration - User interaction (clicking the link) is required - The Emissary web interface is typically accessed only by authent…