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.
{
"cna_assigner": "GitHub_M",
"cwe_ids": [
"CWE-178"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72721.json"
}{
"extracted_events": [
{
"introduced": "0"
},
{
"fixed": "2026.1.6"
},
{
"introduced": "2026.5.0-latest"
},
{
"fixed": "2026.5.2"
},
{
"introduced": "2026.6.0-latest"
},
{
"fixed": "2026.6.1"
},
{
"introduced": "2026.7.0-latest"
},
{
"fixed": "2026.7.0"
}
],
"source": [
"AFFECTED_FIELD",
"REFERENCES"
]
}