Discourse: Encode action_code_who in mention URLs

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-91119
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-24 18:19:06 UTC
Updated2026-09-24 18:19:06 UTC
DescriptionDiscourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the topic small-action and nested-activity-log components interpolated the free-form action_code_who value into mention-link href attributes without URL encoding. A quote-bearing display name could terminate the intended URL attribute and inject attacker-controlled elements into the trusted rendered markup. Although the visible mention text was escaped, the unencoded path component allowed stored HTML injection when another user viewed the affected topic action or activity log. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

Risk And Classification

Primary CVSS: v3.1 6.4 MEDIUM from [email protected]

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

Problem Types: CWE-79 | CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
3.1CNADECLARED6.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Discourse Discourse affected < 2026.8.0 Not specified
CNA Discourse Discourse affected >= 2026.7.0-latest, < 2026.7.2 Not specified
CNA Discourse Discourse affected >= 2026.6.0-latest, < 2026.6.3 Not specified
CNA Discourse Discourse affected >= 2026.1.0-latest, < 2026.1.8 Not specified

References

ReferenceSourceLinkTags
github.com/discourse/discourse/commit/77a81c7a3a7ff9e94b355e32b8f379f2d3... [email protected] github.com
github.com/discourse/discourse/commit/c4748f651d9d2f3a6dd3106a4d5564536c... [email protected] github.com
github.com/discourse/discourse/commit/66653c484cfb91bc346f9a326f6945387f... [email protected] github.com
github.com/discourse/discourse/pull/42882 [email protected] github.com
github.com/discourse/discourse/security/advisories/GHSA-pv3p-p3m9-v8v3 [email protected] github.com
github.com/discourse/discourse/commit/20dbf112760eb1d6a58f2e49aeef754689... [email protected] github.com
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