CVE-2026-72721
Medium
Description
Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, Onebox::DomainChecker.is_blocked? compares hostnames and SiteSetting.blocked_onebox_domains entries case-sensitively, allowing an attacker to bypass configured Onebox domain restrictions by changing character casing in a redirect target hostname. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.
SeverityMedium
CVSS5.3
Exploit probability—
Product
Discourse
PublishedAug 10, 2026
First seenAug 10, 2026
Weakness typeCWE-178CWE-178
How to fix
Sources list no fixed version or patch link for this vulnerability.
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| discourse discourse | < 2026.1.6, >= 2026.5.0-latest, < 2026.5.2, >= 2026.6.0-latest, < 2026.6.1, >= 2026.7.0-latest, < 2026.7.0 | — |
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