Is CVE-2026-54889 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-54889 being exploited in the wild.

How severe is CVE-2026-54889?

Informational severity, with a CVSS score of 5.1, published 29 June 2026.

Which products and versions are affected?

leandrocp mdex 0.8.3 to 0.13.1.

Is there a fix for CVE-2026-54889?

A patch was published on 2026-06-29: Fixed in version 0.13.2 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-54889 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-54889?

Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-54889: leandrocp mdex XSS in Quill Delta conversion

CVE-2026-54889 · Severity: info · CVSS 5.1 · Published 2026-06-29

A vulnerability in the MDEx Markdown library for Elixir could allow attackers to execute malicious scripts in a user's browser. This occurs when the library processes Markdown containing specially crafted links and converts them into a format used by web editors. If an end-user clicks on one of these malicious links, it could lead to unauthorized actions or the theft of sensitive information like session cookies.

Quick answers

Is CVE-2026-54889 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-54889 being exploited in the wild.
How severe is CVE-2026-54889?: Informational severity, with a CVSS score of 5.1, published 29 June 2026.
Which products and versions are affected?: leandrocp mdex 0.8.3 to 0.13.1.
Is there a fix for CVE-2026-54889?: A patch was published on 2026-06-29: Fixed in version 0.13.2 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-54889 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-54889?: Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A Cross-Site Scripting (XSS) vulnerability exists in the 'Elixir.MDEx.DeltaConverter' module of the mdex library. The 'default_convert_node/3' function fails to sanitize or validate URL schemes when processing links, wikilinks, or images, allowing 'javascript:' URIs to be passed directly into the Quill Delta output. When this output is subsequently rendered into HTML by a downstream component (like a Quill client), the malicious URI is placed into 'href' or 'src' attributes. An attacker can exploit this by providing malicious Markdown that, when viewed and interacted with by a user, executes arbitrary JavaScript in the context of the user's session. The issue is fixed in version 0.13.2, which introduces default URL filtering.

Affected products

leandrocp mdex 0.8.3 to 0.13.1

Timeline

2026-06-29: disclosed
2026-06-29: patched: Fixed in version 0.13.2
2026-06-29: advisory

References

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