GHSA-26wg-9xf2-q495

Suggest an improvement
Source
https://github.com/advisories/GHSA-26wg-9xf2-q495
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-26wg-9xf2-q495/GHSA-26wg-9xf2-q495.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-26wg-9xf2-q495
Published
2026-04-14T23:23:01Z
Modified
2026-04-14T23:34:37Z
Severity
  • 8.1 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N CVSS Calculator
Summary
Novu has a XSS sanitization bypass
Details

Summary

XSS sanitization is incomplete, some attributes are missing such as oncontentvisibilityautostatechange=. This allows for the email preview to render HTML that executes arbitrary JavaScript,

Details

Sanitization is implemented here: https://github.com/novuhq/novu/blob/next/libs/application-generic/src/services/sanitize/sanitizer.service.ts

With allowedAttributes: false, all attributes are allowed through sanitize-html. Even dangerous ones like oncontentvisibilityautostatechange=. The DANGEROUS_ATTRIBUTES array tries to handle this by denying more attributes after the fact, but this list is incomplete. I copied all well-known payloads from: https://portswigger.net/web-security/cross-site-scripting/cheat-sheet And found that the oncontentvisibilityautostatechange= attribute isn't detected.

PS. there seems to also be another even more lax sanitizer here, but I wasn't able to figure out where it is used: https://github.com/novuhq/novu/blob/next/packages/framework/src/utils/sanitize.utils.ts

PoC

  1. Create a new workflow and add an Email step
  2. In the body, write the following HTML code:
<a oncontentvisibilityautostatechange="alert(window.origin)" style="display:block;content-visibility:auto">
  1. Wait a second and notice the XSS popup showing the current origin:
image

https://dashboard.novu.co/env/dev_env_gVtdgDEhgf1CetwX/workflows/onboarding-demo-workflow_wf_gVtdh2uV0h7j3ffK/steps/email-step_st_gVtqdgIrOkYVvP9F/editor

Impact

This may look like a Self-XSS similar to https://github.com/novuhq/novu/security/advisories/GHSA-w8vm-jx29-52fr, but it can be more impactful. First of all, if multiple users can access this dashboard, the link above can directly bring the to the email step editor to trigger the XSS. An attacker can also use the Google/GitHub OAuth flows without completing the code callback step, and send that URL to the victim to intentionally log the vicitm into the attacker's account. If the attacker has prepared an XSS payload there, they will now be allowed to view it, so it triggers.

Database specific 
{
    "cwe_ids":  [
        "CWE-79"
    ],
    "github_reviewed":  true,
    "github_reviewed_at":  "2026-04-14T23:23:01Z",
    "nvd_published_at":  null,
    "severity":  "HIGH"
}
References

Affected packages

npm / novu/api

Package

Name
novu/api
View open source insights on deps.dev
Purl
pkg:npm/novu/api

Affected ranges

Type
SEMVER
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
3.15.0

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-26wg-9xf2-q495/GHSA-26wg-9xf2-q495.json"