CVE-2026-33978

Notesnook: Stored XSS in mobile share editor via unescaped web clip title metadata

MEDIUM
6.1
CVSS Score
Published: April 1, 2026 at 04:11 PM UTC
Updated: October 26, 2026 at 10:10 PM UTC
2 products affected across 1 vendorNotesnook MobileNotesnook

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Severity
MEDIUM6.1
Exploit prediction
EPSS 0.3%
SSVC
PoC

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 3.3.17
Affected range stops below 3.3.17, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-79

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