TI-2021-17937 Aliases CVE-2021-41095

XSS via blocked watched word in error message

LOW 28CWE-79Published 2021-09-27 · Updated 2024-08-04

Key facts

Attack vector: Network
Privileges required: None
User interaction: Required
Attack complexity: Low
Impact type: Cross-site scripting
Confidentiality · integrity · availability: Low · Low · None
Fix status: No fix listed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-79.

Summary

Discourse is an open source discussion platform. There is a cross-site scripting (XSS) vulnerability in versions 2.7.7 and earlier of the `stable` branch, versions 2.8.0.beta6 and earlier of the `beta` branch, and versions 2.8.0.beta6 and earlier of the `tests-passed` branch. Rendering of some error messages that contain user input can be susceptible to XSS attacks. This vulnerability only affects sites which have blocked watched words that contain HTML tags, modified or disabled Discourse's default Content Security Policy. This issue is patched in the latest `stable`, `beta` and `tests-passed` versions of Discourse. As a workaround, avoid modifying or disabling Discourse’s default Content Security Policy, and blocking watched words containing HTML tags.

Why it matters now

EPSS 0.00584 48th percentileScored 2026-11-07

Fix No fix listed No fixed version in the sources yet

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
discourse	discourse	up to 2.7.7; 2.8.0.beta1 – 2.8.0.beta6	—	No fix listed	CNA

discourse Vendordiscourse Affected up to 2.7.7; 2.8.0.beta1 – 2.8.0.beta6 Fixed in — No fix listed CNA

CPE configurations NVD · 7

CPE	Versions	Role	Vendor
cpe:2.3:a:discourse:discourse::::::::	up to 2.7.7	Vulnerable	discourse
cpe:2.3:a:discourse:discourse:2.8.0:beta1::::::	2.8.0 beta1	Vulnerable	discourse
cpe:2.3:a:discourse:discourse:2.8.0:beta2::::::	2.8.0 beta2	Vulnerable	discourse
cpe:2.3:a:discourse:discourse:2.8.0:beta3::::::	2.8.0 beta3	Vulnerable	discourse
cpe:2.3:a:discourse:discourse:2.8.0:beta4::::::	2.8.0 beta4	Vulnerable	discourse
cpe:2.3:a:discourse:discourse:2.8.0:beta5::::::	2.8.0 beta5	Vulnerable	discourse
cpe:2.3:a:discourse:discourse:2.8.0:beta6::::::	2.8.0 beta6	Vulnerable	discourse

cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:* Versions up to 2.7.7 Vulnerable ·discourse
cpe:2.3:a:discourse:discourse:2.8.0:beta1:*:*:*:*:*:* Versions 2.8.0 beta1 Vulnerable ·discourse
cpe:2.3:a:discourse:discourse:2.8.0:beta2:*:*:*:*:*:* Versions 2.8.0 beta2 Vulnerable ·discourse
cpe:2.3:a:discourse:discourse:2.8.0:beta3:*:*:*:*:*:* Versions 2.8.0 beta3 Vulnerable ·discourse
cpe:2.3:a:discourse:discourse:2.8.0:beta4:*:*:*:*:*:* Versions 2.8.0 beta4 Vulnerable ·discourse
cpe:2.3:a:discourse:discourse:2.8.0:beta5:*:*:*:*:*:* Versions 2.8.0 beta5 Vulnerable ·discourse
cpe:2.3:a:discourse:discourse:2.8.0:beta6:*:*:*:*:*:* Versions 2.8.0 beta6 Vulnerable ·discourse

Remediation

No fixed version listed by the sources yet.

Timeline

2026-10-02 Threatist record created from CVE-2021-41095

References

Patch 1

https://github.com/discourse/discourse/pull/14434/commits/40b776b9d39c41d9273d01eecf8fe03aa39fcb59

Advisory 1

https://github.com/discourse/discourse/security/advisories/GHSA-qvqx-2h7w-m479

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

See all 262 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences