# CVE-2026-33976: Notesnook vulnerable to RCE via stored XSS in Web Clipper rendering

> Attackers can achieve remote code execution in the Notesnook desktop app via stored XSS in the Web Clipper due to unsafe HTML rendering and Electron configuration.

- **Severity:** Critical 9.7 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H`)
- **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:** No
- **Published:** 27 Mar 2026
- **Updated:** 3 Apr 2026
- **Also known as:** GHSA-f42f-phvp-43x5

## What is CVE-2026-33976?

CVE-2026-33976 is a critical cross-site scripting vulnerability in streetwriters Notesnook Web/Desktop, published on 27 Mar 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

Notesnook is a note-taking app. Prior to version 3.3.11 on Web/Desktop and 3.3.17 on Android/iOS, a stored XSS in the Web Clipper rendering flow can be escalated to remote code execution in the desktop app. The root cause is that the clipper preserves attacker-controlled attributes from the source page’s root element and stores them inside web-clip HTML. When the clip is later opened, Notesnook renders that HTML into a same-origin, unsandboxed iframe using `contentDocument.write(...)`. Event-handler attributes such as `onload`, `onclick`, or `onmouseover` execute in the Notesnook origin. In the desktop app, this becomes RCE because Electron is configured with `nodeIntegration: true` and `contextIsolation: false`. Version 3.3.11 Web/Desktop and 3.3.17 on Android/iOS patch the issue.

Weakness: CWE-94 (Improper Control of Generation of Code), CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-33976?

It affects 2 products.


Products: Streetwriters Notesnook Desktop, Streetwriters Notesnook Mobile.

## How do I fix CVE-2026-33976?

No fix has been published for CVE-2026-33976 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-33976 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33976 exists.

## Other vulnerabilities in streetwriters Notesnook Web/Desktop

- [CVE-2026-42090](https://insights.sbomify.com/CVE-2026-42090/): Notesnook: RCE via stored XSS in note export rendering (critical 9.6)
- [CVE-2026-33955](https://insights.sbomify.com/CVE-2026-33955/): Notesnook vulnerable to RCE via stored XSS in Note History diff viewer (high 8.6)
- [CVE-2026-31876](https://insights.sbomify.com/CVE-2026-31876/): Notesnook has Stored XSS via unsanitized Twitter/X embed URL in editor (`tweetToEmbed`) (medium 5.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33976 and fix it if it is affected.

What it is: CVE-2026-33976 is a critical cross-site scripting vulnerability in streetwriters Notesnook Web/Desktop, published on 27 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33976 exists.

Affected product: streetwriters Notesnook Web/Desktop. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-33976/ (Markdown: https://insights.sbomify.com/CVE-2026-33976/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33976
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33976
- OSV: https://osv.dev/vulnerability/CVE-2026-33976

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33976/
Summaries are generated and may contain mistakes; the official description above is the record.