Discourse: Stored HTML injection in video notification emails

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-91120
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, provider-controlled video titles in lazy video embeds could be reparsed as HTML when Discourse generated notification emails or chat summaries. A user with standard posting privileges could create a post for an enabled YouTube, Vimeo, or TikTok provider whose title contained markup, and the email and chat-summary rendering path would place that markup into the output instead of treating it solely as text. Recipients using HTML-capable email clients could see injected content, potentially including event handlers, but the issue did not directly expose a Discourse browser session or affect the forum page itself. Lazy video embeds must be enabled, which is the default configuration. 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 5.4 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/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]Secondary5.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
3.1CNADECLARED5.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

CVSS v3.1 Breakdown

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

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/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/security/advisories/GHSA-h7cg-2vww-m45c [email protected] github.com
github.com/discourse/discourse/commit/6bf1cdcb3ae1aa146e1fd953a62046bf4a... [email protected] github.com
github.com/discourse/discourse/pull/42882 [email protected] github.com
github.com/discourse/discourse/commit/e7de8285203a2edf85beff3b951e66aeb7... [email protected] github.com
github.com/discourse/discourse/commit/ed8b47df80bcc9f0bd70773fc399c9386f... [email protected] github.com
github.com/discourse/discourse/commit/8338919df4ecbd0fb85314b762772cc033... [email protected] github.com
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