CVE-2026-55105 Joplin: Fountain embeds allow arbitrary script execution in published notes and the note viewer
Attackers can execute arbitrary scripts via malicious Fountain code blocks in Joplin notes, potentially reading sensitive data or taking over accounts.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-55105?
CVE-2026-55105 is a high-severity cross-site scripting vulnerability in laurent22 joplin, published on 21 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
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.
Weakness: CWE-79
Which versions are affected by CVE-2026-55105?
How do I fix CVE-2026-55105?
No fix has been published for CVE-2026-55105 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-55105 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55105 exists.
Sources
Also known as GHSA-f7q3-3grx-6wg9.