CVE-2026-59830Network attack vectorHinoki check available

Stored XSS via unescaped post-action actor name

Published Sep 21, 2026 · Updated Sep 21, 2026

Stored XSS in Discourse before 2026.7.0 allows remote authenticated users to execute script in another user's browser via a crafted display name. The post-action component interpolates the unescaped actor name into an HTML string and passes the result to trustHTML, causing persisted markup to be treated as trusted content. An attacker needs control of an account display name, and execution occurs when another user views an affected activity stream.

CVSS severity5.4
Medium
EPSS probability0.29%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Stored XSS in Discourse before 2026.7.0 allows remote authenticated users to execute script in another user's browser via a crafted display name. The post-action component interpolates the unescaped actor name into an HTML string and passes the result to trustHTML, causing persisted markup to be treated as trusted content. An attacker needs control of an account display name, and execution occurs when another user views an affected activity stream.

The record

CVE
CVE-2026-59830
Published
Sep 21, 2026
Updated
Sep 21, 2026
Vendor
Discourse
Product
Discourse
Classifications
T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 21, 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=< 2026.7.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Discourse · Discourseversion=< 2026.7.0

Published CVSS scores

5.4GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A: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.

Activity data is delayed. The latest report is Sep 28, 2026.

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

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1059.007Command and Scripting Interpreter: JavaScript/JScript

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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