Stored DOM-based XSS (without CSP) via video placeholders in Discourse
Priority LOW 29CWE-79Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Cross-site scripting
- Confidentiality · integrity · availability
- Low · None · Low
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-79.
Summary
Discourse is an open source platform for community discussion. In affected versions an attacker can execute arbitrary JavaScript on users' browsers by posting a malicious video placeholder html element. This issue only affects sites with CSP disabled. This problem has been patched in the latest version of Discourse. Users are advised to upgrade. Users unable to upgrade should enable CSP.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00362 30th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| discourse | discourse | stable: <= 3.3.3; beta: <= 3.4.0.beta3; tests-passed: <= 3.4.0.beta3 | — | No fix listed | CNA |
- discourse Vendordiscourse Affected stable: <= 3.3.3; beta: <= 3.4.0.beta3; tests-passed: <= 3.4.0.beta3 Fixed in — No fix listed CNA
CPE configurations NVD · 5
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:discourse:discourse:*:*:*:*:stable:*:*:* | before 3.3.4 | Vulnerable | discourse |
| cpe:2.3:a:discourse:discourse:*:*:*:*:beta:*:*:* | before 3.4.0 | Vulnerable | discourse |
| cpe:2.3:a:discourse:discourse:3.4.0:beta1:*:*:beta:*:*:* | 3.4.0 beta1 | Vulnerable | discourse |
| cpe:2.3:a:discourse:discourse:3.4.0:beta2:*:*:beta:*:*:* | 3.4.0 beta2 | Vulnerable | discourse |
| cpe:2.3:a:discourse:discourse:3.4.0:beta3:*:*:beta:*:*:* | 3.4.0 beta3 | Vulnerable | discourse |
- cpe:2.3:a:discourse:discourse:*:*:*:*:stable:*:*:* Versions before 3.3.4 Vulnerable ·discourse
- cpe:2.3:a:discourse:discourse:*:*:*:*:beta:*:*:* Versions before 3.4.0 Vulnerable ·discourse
- cpe:2.3:a:discourse:discourse:3.4.0:beta1:*:*:beta:*:*:* Versions 3.4.0 beta1 Vulnerable ·discourse
- cpe:2.3:a:discourse:discourse:3.4.0:beta2:*:*:beta:*:*:* Versions 3.4.0 beta2 Vulnerable ·discourse
- cpe:2.3:a:discourse:discourse:3.4.0:beta3:*:*:beta:*:*:* Versions 3.4.0 beta3 Vulnerable ·discourse
Remediation
No fixed version listed by the sources yet.
Timeline
- 2026-10-02 Threatist record created from CVE-2025-22602
References
More Discourse vulnerabilities
- TI-2021-19656 Denial of Service in discourse CVSS 3.1MEDIUM 6.8
- TI-2024-36150 Potential Backup file leaked via Nginx in Discourse CVSS 3.1HIGH 7.5
- TI-2021-18002 RCE via malicious SNS subscription payload CVSS 3.1CRITICAL 10.0
- TI-2026-24651 Discourse: Open redirect via `sso_destination_url` cookie in `enter` CVSS 4.0MEDIUM 5.1
- TI-2026-22278 Discourse leaks private topic title and post excerpt via user action API endpoint CVSS 4.0HIGH 8.7
- TI-2023-24152 Unauthenticated access to new private chat messages in Discourse CVSS 3.1HIGH 7.5
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences