CVE-2026-55424Network attack vector

Stored XSS via unescaped featured link

Published Jul 9, 2026 · Updated Jul 9, 2026

Stored XSS in the topic-list featured-link renderer in Discourse allows remote authenticated users to inject JavaScript into viewers' sessions. The renderer interpolates a minimally processed featured_link into trusted anchor markup without escaping its href, rel, target, and domain values, so embedded quotes can create an event-handler attribute. Exploitation requires permission to set a featured link, a viewer who loads the affected topic list, and a site whose default CSP was disabled or changed to permit inline scripts.

CVSS severity7.4
High
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in the topic-list featured-link renderer in Discourse allows remote authenticated users to inject JavaScript into viewers' sessions. The renderer interpolates a minimally processed featured_link into trusted anchor markup without escaping its href, rel, target, and domain values, so embedded quotes can create an event-handler attribute. Exploitation requires permission to set a featured link, a viewer who loads the affected topic list, and a site whose default CSP was disabled or changed to permit inline scripts.

The record

CVE
CVE-2026-55424
Published
Jul 9, 2026
Updated
Jul 9, 2026
Vendor
Discourse
Product
Discourse
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 2026.1.0-latest, < 2026.1.5
  2. Affected versionversion=>= 2026.4.0-latest, < 2026.4.2
  3. Affected versionversion=>= 2026.5.0-latest, < 2026.5.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Discourse · Discourseversion=>= 2026.1.0-latest, < 2026.1.5; version=>= 2026.4.0-latest, < 2026.4.2; version=>= 2026.5.0-latest, < 2026.5.1

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
7.4GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript/JScript

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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