Vulnerability · Published Sep 21, 2026 · Assigned by GitHub_M

CVE-2026-55105Joplin: Fountain embeds allow arbitrary script execution in published notes and the note viewer

High 7.7

In plain English

A high-severity cross-site scripting in joplin from laurent22. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 43% of all known vulnerabilities).

Severity (CVSS 3.1)7.7High

Exploit odds (30 days)0.5%top 57.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Joplin is an open source note-taking and to-do application that organises notes and lists into notebooks. Prior to 3.6.15 and 3.7.2, packages/renderer/MdToHtml/rules/fountain.ts passes HTML generated by the vendored fountain.js renderer into note output without sanitizing it. A malicious Fountain code block can therefore execute script when Fountain rendering is enabled in desktop or mobile clients, or when a note is published through Joplin Server where Fountain rendering is enabled by default. The script can read content subsequently loaded in the reused note viewer or, when published notes are served from the same domain as server content, access data available to an authenticated browser in the server origin. This issue is fixed in versions 3.6.15 and 3.7.2.

Affected products (as reported)

Vendor	Product	Versions
laurent22	joplin	< 3.6.15>= 3.7.0, < 3.7.2

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

References

https://github.com/laurent22/joplin/security/advisories/GHSA-f7q3-3grx-6wg9 x_refsource_CONFIRM
https://github.com/laurent22/joplin/pull/15659 x_refsource_MISC
https://github.com/laurent22/joplin/commit/8e0812de9d79d1f0698bb76a8c5d7e991df9748d x_refsource_MISC