Discourse is an open source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2, insufficient cleanup in the default Codepen allowed iframes value allows an attacker to trick a user into changing the URL of the main page. This issue has been fixed in versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2. To workaround this issue, remove Codepen from the list of allowed iframes.
{
"cna_assigner": "GitHub_M",
"cwe_ids": [
"CWE-80"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27166.json"
}{
"extracted_events": [
{
"cpe": "cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "0"
},
{
"fixed": "2026.3.0"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "2026.1.0"
},
{
"fixed": "2026.1.2"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "2026.2.0"
},
{
"fixed": "2026.2.1"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:discourse:discourse:2026.3.0:*:*:*:latest:*:*:*",
"range": [
{
"introduced": "2026.3.0"
},
{
"last_affected": "2026.3.0"
}
],
"source": "CPE_STRING"
},
{
"range": [
{
"fixed": "c4762a4fac2f61f52f325396b11d3aeb955ea925"
}
],
"source": "REFERENCES_COMMIT"
}
]
}