CVE-2021-39161 - CVE House
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Status published Medium CVE-2021-39161

Cross-site scripting via category name in Discourse

Vulnerability Description

Discourse is an open source platform for community discussion. In affected versions category names can be used for Cross-site scripting(XSS) attacks. This is mitigated by Discourse's default Content Security Policy and this vulnerability only affects sites which have modified or disabled or changed Discourse's default Content Security Policy have allowed for moderators to modify categories. This issue is patched in the latest stable, beta and tests-passed versions of Discourse. Users are advised to ensure that the Content Security Policy is enabled, and has not been modified in a way which would make it more vulnerable to XSS attacks.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

No credits recorded in the NVD database.

References

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Affected Vendor

Affected Software

discourse
Vulnerable Versions:
< 2.7.8, >= 2.8.0.beta1, < 2.8.0.beta4

Timeline

Official Publish: August 26th, 2021
Last Modified: August 4th, 2024
Added to House: July 21st, 2026

CVSS Vectors

V3: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N

Weaknesses (CWE)

CWE-79

MITRE ATT&CK TTPs

T1189 Drive-by Compromise
Initial Access
T1059.007 JavaScript
Execution
T1539 Steal Web Session Cookie
Collection
T1213 Data from Information Repositories
Collection
T1567 Exfiltration Over Web Service
Exfiltration
T1491.001 Defacement
Impact