CVE-2026-33411
Stored XSS in Discourse Topic Titles Affects Post Streams
Publication date: 2026-03-20
Last updated on: 2026-03-24
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| discourse | discourse | From 2026.1.0 (inc) to 2026.1.2 (exc) |
| discourse | discourse | From 2026.2.0 (inc) to 2026.2.1 (exc) |
| discourse | discourse | 2026.3.0 |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-79 | The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability is a stored Cross-Site Scripting (XSS) issue found in the Discourse open-source discussion platform. It affects versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2. The vulnerability exists in the topic titles for the solved posts stream, where malicious scripts can be injected and stored. When other users view these topic titles, the malicious scripts may execute in their browsers.
A patch addressing this vulnerability is included in versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2. As a temporary workaround, enabling and properly configuring the Content Security Policy (CSP) can help mitigate the risk by restricting the execution of unauthorized scripts.
How can this vulnerability impact me? :
This stored XSS vulnerability can allow attackers to execute malicious scripts in the browsers of users who view the affected topic titles. This can lead to unauthorized actions such as stealing user credentials, session hijacking, defacement of content, or spreading malware.
The CVSS base score of 5.4 indicates a medium severity, meaning the impact is significant but not critical. The vulnerability requires network access and low privileges but does not require user interaction.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, ensure that your Discourse installation is updated to one of the patched versions: 2026.3.0-latest.1, 2026.2.1, or 2026.1.2.
As a workaround, make sure that the Content Security Policy (CSP) is enabled and has not been modified in a way that would increase vulnerability to XSS attacks.