{"id":"BIT-discourse-2026-72721","summary":"Discourse: Onebox Domain Blocklist Bypass via Case-Sensitive Comparison","details":"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.","aliases":["CVE-2026-72721","GHSA-3x7x-24rq-h5j6"],"modified":"2026-08-17T08:10:35.880164157Z","published":"2026-08-17T05:44:20.901Z","database_specific":{"severity":"Medium","cpes":["cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*"]},"references":[{"type":"WEB","url":"https://github.com/discourse/discourse/commit/a3e10759fef47f03d450649bb51d9e84f4c68b8f"},{"type":"WEB","url":"https://github.com/discourse/discourse/commit/c2eb6b0e5597d6f28f4be739b83300bc9c69e3cd"},{"type":"WEB","url":"https://github.com/discourse/discourse/commit/caa615c371b1696982ee11ac8f3558f0f8ced584"},{"type":"WEB","url":"https://github.com/discourse/discourse/commit/f503971d311b7b0dfdb751ee8cfd67e8cb99f5c5"},{"type":"WEB","url":"https://github.com/discourse/discourse/pull/42091"},{"type":"WEB","url":"https://github.com/discourse/discourse/pull/42092"},{"type":"WEB","url":"https://github.com/discourse/discourse/pull/42093"},{"type":"WEB","url":"https://github.com/discourse/discourse/pull/42094"},{"type":"WEB","url":"https://github.com/discourse/discourse/security/advisories/GHSA-3x7x-24rq-h5j6"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72721"}],"affected":[{"package":{"name":"discourse","ecosystem":"Bitnami","purl":"pkg:bitnami/discourse"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2026.1.6"},{"introduced":"2026.5.0"},{"fixed":"2026.5.2"},{"introduced":"2026.6.0"},{"fixed":"2026.6.1"}]}],"database_specific":{"source":"https://github.com/bitnami/vulndb/tree/main/data/discourse/BIT-discourse-2026-72721.json"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"}]}],"schema_version":"1.9.0"}