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Description

Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the `allowed_spam_host_domains` check used `String#end_with?` without domain boundary validation, allowing domains like `attacker-example.com` to bypass spam protection when `example.com` was allowlisted. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 require exact match or proper subdomain match (preceded by `.`) to prevent suffix-based bypass of `newuser_spam_host_threshold`. No known workarounds are available.

PUBLISHED Reserved 2026-03-19 | Published 2026-03-19 | Updated 2026-03-20 | Assigner GitHub_M




MEDIUM: 4.3CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Problem types

CWE-284: Improper Access Control

Product status

>= 2026.1.0-latest, < 2026.1.2
affected

>= 2026.2.0-latest, < 2026.2.1
affected

= 2026.3.0-latest
affected

References

github.com/...course/security/advisories/GHSA-95r5-p6qr-hgw6

github.com/...ommit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2

github.com/...ommit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02

github.com/...ommit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8e

cve.org (CVE-2026-33393)

nvd.nist.gov (CVE-2026-33393)

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