CVE-2026-33395Network attack vector

Stored click-triggered XSS via unsanitized SVG links

Published Mar 19, 2026 · Updated Mar 19, 2026

Stored XSS in Discourse before 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 allows remote authenticated users to run JavaScript. The Graphviz post processor embeds user-controlled DOT URL attributes as SVG anchor href values without restricting javascript: and other executable schemes. Exploitation requires Graphviz enabled, CSP disabled, and a victim to click the rendered link, which executes code in that viewer's Discourse origin.

CVSS severity4.4
Medium
EPSS probability0.21%
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 Discourse before 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 allows remote authenticated users to run JavaScript. The Graphviz post processor embeds user-controlled DOT URL attributes as SVG anchor href values without restricting javascript: and other executable schemes. Exploitation requires Graphviz enabled, CSP disabled, and a victim to click the rendered link, which executes code in that viewer's Discourse origin.

The record

CVE
CVE-2026-33395
Published
Mar 19, 2026
Updated
Mar 19, 2026
Vendor
Discourse
Product
Discourse
Classifications
CWE-79, T1204.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 19, 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, < 2026.1.2
  2. Affected versionversion=>= 2026.2.0-latest, < 2026.2.1
  3. Affected versionversion== 2026.3.0-latest

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Discourse · Discourseversion=>= 2026.1.0-latest, < 2026.1.2; version=>= 2026.2.0-latest, < 2026.2.1; version== 2026.3.0-latest

Published CVSS scores

4.4GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N
5.4NIST NVDCVSS: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.

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')
T1204.001User Execution: Malicious Link

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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