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.
{
"cwe_ids": [
"CWE-80"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27166.json",
"cna_assigner": "GitHub_M"
}{
"versions": [
{
"introduced": "0"
},
{
"fixed": "2026.3.0-latest.1"
}
]
}