CVE-2025-58054: Discourse is vulnerable to XSS when quoting chat messages

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-10-01 · updated 2026-10-19
Weakness: CWE-80

Description

Discourse is an open-source community discussion platform. Versions 3.5.0 and below are vulnerable to XSS attacks through parsing and rendering of chat channel titles and chat thread titles via the quote message functionality when using the rich text editor. This issue is fixed in version 3.5.1.

Affected products

discourse: before 3.5.0; before 3.6.0; 3.6.0-beta1 — fixed in 3.5.0, 3.6.0

How to fix

Upgrade to a fixed version: discourse 3.5.0, 3.6.0. Check the vendor advisory for mitigations.

References

https://github.com/discourse/discourse/commit/3a224fd546d894ee408e7414b6879e814a792f91
https://github.com/discourse/discourse/security/advisories/GHSA-7p47-8m82-m2vf

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