CVE-2026-111059 Mercury: Stored / DOM Cross-Site Scripting (XSS): mr.Markdown renders untrusted content as raw, unsanitized HTML
Attackers can inject malicious scripts via Markdown content in Mercury applications, leading to code execution in victim browsers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-111059?
CVE-2026-111059 is a medium-severity cross-site scripting vulnerability in mljar mercury, published on 19 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Mercury is a Python framework for sharing Jupyter notebooks as web applications and dashboards. From 3.0.0 until 3.2.11, mr.Markdown converts attacker-controlled Markdown to HTML without sanitizing raw HTML before assigning it to an ipywidgets.HTML sink. Event-handler attributes and other active HTML can therefore reach the DOM and execute when another user views the application. This issue is fixed in version 3.2.11.
Which versions are affected by CVE-2026-111059?
2 open source packages ship an affected version, including mercury.
| Package | Affected | Fixed in |
|---|---|---|
mercury PyPI | From 3.0.0 | 3.2.11 |
mercury PyPI | From 3.0.0 | 3.2.11 |
How do I fix CVE-2026-111059?
Upgrade mercury to 3.2.11 or later.
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-2026-111059 being exploited?
There is no known exploitation of CVE-2026-111059 in the wild and no public exploit code.
Sources
Also known as GHSA-2658-85cv-9wwq.