Description
Discourse Mermaid (discourse-mermaid-theme-component) allows users of Discourse, open-source forum software, to create graphs using the Mermaid syntax. Users of discourse-mermaid-theme-component version 1.0.0 who can create posts are able to inject arbitrary HTML on that post. The issue has been fixed on the `main` branch of the GitHub repository, with 1.1.0 named as a patched version. Admins can update the theme component through the admin UI. As a workaround, admins can temporarily disable discourse-mermaid-theme-component.
References (3)
Core 3
Core References
Third Party Advisory x_refsource_confirm
https://github.com/discourse/discourse-mermaid-theme-component/security/advisories/GHSA-8437-hgcm-p3q3
Patch, Third Party Advisory x_refsource_misc
https://github.com/discourse/discourse-mermaid-theme-component/pull/14
Patch, Third Party Advisory x_refsource_misc
https://github.com/discourse/discourse-mermaid-theme-component/commit/c10bc4a08bf865cee20e5d5dffba535762813f0f
Scores
CVSS v3
5.0
EPSS
0.0039
EPSS Percentile
60.2%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
no
Technical Impact
partial
Details
CWE
CWE-74
CWE-79
Status
published
Products (1)
discourse/mermaid
1.0.0 - 1.1.0
Published
Jan 04, 2023
Tracked Since
Feb 18, 2026