CVE-2026-111059: Mercury: Stored / DOM Cross-Site Scripting (XSS): mr.Markdown renders untrusted content as raw, unsanitized HTML

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-19 · updated 2026-10-20
Weakness: CWE-79

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.

Affected products

mljar mercury: from 3.0.0, < 3.2.11

References

https://github.com/mljar/mercury/commit/c798a85924e6614c6fea7afe5a560e4554a1d09b
https://github.com/mljar/mercury/releases/tag/v3.2.11
https://github.com/mljar/mercury/security/advisories/GHSA-2658-85cv-9wwq

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