# CVE-2026-40262: Note Mark has Stored XSS via Unrestricted Asset Upload

Source: https://junglewise.ai/threats/cve-2026-40262-note-mark-has-stored-xss-via-unrestricted-asset-upload  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-17. Updated: 2026-05-11  
License: CC BY 4.0 with a link back

CVE-2026-40262 · Severity: high · CVSS 8.7 · Published 2026-04-17

Note Mark is an open-source note-taking application. In versions 0.19.1 and prior, the asset delivery handler serves uploaded files inline and relies on magic-byte detection for content type, which does not identify text-based formats such as HTML, SVG, or XHTML. These files are served with an empty Content-Type, no X-Content-Type-Options: nosniff header, and inline disposition, allowing browsers to sniff and render active content. An authenticated user can upload an HTML or SVG file containing JavaScript as a note asset, and when a victim navigates to the asset URL, the script executes under the application's origin with access to the victim's authenticated session and API actions. This issue has been fixed in version 0.19.2.

Technologies: [github.com/enchant97/note-mark/backend (Go)](https://junglewise.ai/threats/technologies/github-com-enchant97-note-mark-backend). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-40262 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-40262 being exploited in the wild.

**How severe is CVE-2026-40262?** High severity, with a CVSS score of 8.7, published 17 April 2026.

**Which products and versions are affected?** github.com/enchant97/note-mark/backend (Go) < 0.0.0-20260411145018-6bb62842ccb9, SEMVER:introduced=0,fixed=0.0.0-20260411145018-6bb62842ccb9.

**Is there a fix for CVE-2026-40262?** Yes. github.com/enchant97/note-mark/backend (Go): upgrade to 0.0.0-20260411145018-6bb62842ccb9 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2026-40262?** Check whether you run github.com/enchant97/note-mark/backend (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/enchant97/note-mark/backend (Go): upgrade to 0.0.0-20260411145018-6bb62842ccb9 or later

  ```sh
  go get github.com/enchant97/note-mark/backend@v0.0.0-20260411145018-6bb62842ccb9
  ```


## Affected products

- github.com/enchant97/note-mark/backend (Go) < 0.0.0-20260411145018-6bb62842ccb9, SEMVER:introduced=0,fixed=0.0.0-20260411145018-6bb62842ccb9

## Identifiers

- CVE-2026-40262
- GHSA-9pr4-rf97-79qh
- GO-2026-5295

## References

- [https://api.github.com/users/QiaoNPC](https://api.github.com/users/QiaoNPC)
- [https://github.com/QiaoNPC](https://github.com/QiaoNPC)
- [https://api.github.com/users/QiaoNPC/gists%7B/gist_id%7D](https://api.github.com/users/QiaoNPC/gists%7B/gist_id%7D)
- [https://api.github.com/users/QiaoNPC/repos](https://api.github.com/users/QiaoNPC/repos)
- [https://avatars.githubusercontent.com/u/165803850?v=4](https://avatars.githubusercontent.com/u/165803850?v=4)
- [https://api.github.com/users/QiaoNPC/events%7B/privacy%7D](https://api.github.com/users/QiaoNPC/events%7B/privacy%7D)

## Related threats

- [Note Mark path traversal in migrate export via unsanitized slugs](https://junglewise.ai/threats/cve-2026-50553-note-mark-path-traversal-in-migrate-export-via-unsanitized-slugs)
- [Note Mark information disclosure of soft-deleted notes in public books](https://junglewise.ai/threats/cve-2026-50554-note-mark-information-disclosure-of-soft-deleted-notes-in-public)
- [enchant97 Note Mark weak JWT secret allows account takeover](https://junglewise.ai/threats/cve-2026-44523-enchant97-note-mark-weak-jwt-secret-allows-account-takeover)
- [enchant97 Note Mark path traversal in asset upload](https://junglewise.ai/threats/cve-2026-44522-enchant97-note-mark-path-traversal-in-asset-upload)
- [Note Mark: Unauthenticated read of notes and assets in soft-deleted public books](https://junglewise.ai/threats/cve-2026-41572-note-mark-unauthenticated-read-of-notes-and-assets-in-soft)