Is CVE-2026-72721 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-72721?

CVE-2026-72721 has a CVSS v3 severity of MEDIUM (5.3).

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CVE-2026-72721

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.