Executive brief
Novu is a notification and inbox service that allows organizations to send and manage in-app notifications to users. A low-privilege workflow author can inject malicious JavaScript into notifications that executes in the browser of any recipient who clicks the notification, potentially allowing theft of session tokens, authentication cookies, or execution of actions on behalf of the victim in the application's origin.
Technical details
The vulnerability is a stored cross-site scripting (XSS) flaw in the `@novu/js` In-App Inbox renderer. The `navigate()` function in the notification click handler passes a notification's `redirect.url` to `window.open()` without validating the URL scheme, allowing `javascript:` URLs to be executed. A workflow author (authenticated) can craft a v1 in-app workflow with a CTA containing `url: "javascript:<payload>"` and `target: "_self"`. The server-side notification mapper copies these values without scheme validation (v2 schema does validate via `redirectUrlRegex`, but v1 does not), and the client renderer invokes `window.open(url, "_self", "noopener,noreferrer")`. In Chromium browsers, `javascript:` URLs opened with `target="_self"` execute in the current document origin. The attack requires an authenticated workflow author and a Chromium-based browser on the victim side; victims of the self-hosted dashboard can have their session tokens exfiltrated from `localStorage['self-hosted-jwt']` and used to impersonate other members or admins.
Affected products
- Novu Novu API <= 3.15.0
- Novu @novu/js <= 3.15.0
- Novu @novu/react <= 3.15.0
Timeline
- 2026-09-22: disclosed: Advisory published