{"id":"CVE-2026-72721","title":"Discourse is an open-source discussion platform","summary":"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 attac…","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","cwe":["CWE-178"],"published":"2026-08-10","updated":"2026-09-08","sourceUpdated":"2026-09-08T20:54:37.790","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-72721","references":[{"url":"https://github.com/discourse/discourse/commit/a3e10759fef47f03d450649bb51d9e84f4c68b8f","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/commit/c2eb6b0e5597d6f28f4be739b83300bc9c69e3cd","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/commit/caa615c371b1696982ee11ac8f3558f0f8ced584","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/commit/f503971d311b7b0dfdb751ee8cfd67e8cb99f5c5","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/pull/42091","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/pull/42092","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/pull/42093","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/pull/42094","label":"security-advisories@github.com"},{"url":"https://github.com/discourse/discourse/security/advisories/GHSA-3x7x-24rq-h5j6","label":"security-advisories@github.com"}],"tags":["nvd"],"epss":0.00585,"epssPercentile":0.45669,"ingestedAt":"2026-09-08T21:11:12.272Z","slug":"CVE-2026-72721","body":"## Overview\n\nDiscourse 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}