laurent22 Joplin up to 3.6.14/3.7.1 Fountain Renderer fountain.ts mdToHtml cross site scripting

Summaryinfo

A vulnerability was found in laurent22 Joplin up to 3.6.14/3.7.1. It has been classified as problematic. Affected by this vulnerability is the function mdToHtml of the file packages/renderer/MdToHtml/rules/fountain.ts of the component Fountain Renderer. The manipulation leads to cross site scripting. This vulnerability is uniquely identified as CVE-2026-55105. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in laurent22 Joplin up to 3.6.14/3.7.1. This issue affects the function mdToHtml of the file packages/renderer/MdToHtml/rules/fountain.ts of the component Fountain Renderer. The manipulation with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-55105 since 06/16/2026. The exploitation is known to be easy. The attack may be initiated remotely. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading to version 3.6.15 or 3.7.2 eliminates this vulnerability.

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Productinfo

Vendor

• laurent22

Name

• Joplin

Version

• 3.6.0
• 3.6.1
• 3.6.2
• 3.6.3
• 3.6.4
• 3.6.5
• 3.6.6
• 3.6.7
• 3.6.8
• 3.6.9
• 3.6.10
• 3.6.11
• 3.6.12
• 3.6.13
• 3.6.14
• 3.7.0
• 3.7.1

Website

• Product: https://github.com/laurent22/joplin/

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