Discourse: Block post iframes whose encoded userinfo bypasses the allowed_iframes allowlist
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the Discourse post sanitizer allowed a stored cross-origin iframe to bypass the allowed_iframes prefix policy when the iframe src contained encoded userinfo. The sanitizer validated a decoded form differently from the stored iframe src, allowing the browser to interpret an attacker-controlled host while the allowlist check accepted the encoded URL as an allowed prefix. An authenticated user with posting privileges could persist the iframe in a post and cause attacker-controlled cross-origin content to be rendered. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
CVE-2026-91134
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-91134
discourse
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "discourse",
"product": "discourse",
"versions": [
{
"status": "affected",
"version": "< 2026.8.0"
},
{
"status": "affected",
"version": ">= 2026.7.0-latest, < 2026.7.2"
},
{
"status": "affected",
"version": ">= 2026.6.0-latest, < 2026.6.3"
},
{
"status": "affected",
"version": ">= 2026.1.0-latest, < 2026.1.8"
}
]
}
]- Related CVEs
- CVE-2026-91134
Source reference:
/cveMetadata/cveId
Publisher severity
medium
Source reference: /containers/cna/metrics
- Event
- #3387 · Revision 1
- Added to Heist Feed
- Publisher date