Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, sites using wildcard patterns in the allowed_iframes setting could accept a crafted iframe URL whose allowlisted suffix appeared after a URL authority separator. The wildcard origin check matched the allowed domain text, while browser URL parsing selected a different attacker-controlled origin. A user with posting privileges could exploit the flaw through a post or a Onebox oEmbed response and cause an attacker-controlled iframe to be rendered independently of the allowlisted domain. Successful exploitation requires a site-configured wildcard iframe pattern and the ability to create a post or trigger an oEmbed request for an attacker-controlled URL. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

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History

Thu, 24 Sep 2026 20:00:00 +0000

Type Values Removed Values Added
First Time appeared Discourse
Discourse discourse
Vendors & Products Discourse
Discourse discourse

Thu, 24 Sep 2026 17:00:00 +0000

Type Values Removed Values Added
Description Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, sites using wildcard patterns in the allowed_iframes setting could accept a crafted iframe URL whose allowlisted suffix appeared after a URL authority separator. The wildcard origin check matched the allowed domain text, while browser URL parsing selected a different attacker-controlled origin. A user with posting privileges could exploit the flaw through a post or a Onebox oEmbed response and cause an attacker-controlled iframe to be rendered independently of the allowlisted domain. Successful exploitation requires a site-configured wildcard iframe pattern and the ability to create a post or trigger an oEmbed request for an attacker-controlled URL. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
Title Discourse: Wildcard iframe origin allowlist bypass via authority separators
Weaknesses CWE-346
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-24T16:57:43.082Z

Reserved: 2026-09-14T19:36:48.844Z

Link: CVE-2026-91132

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Deferred

Published: 2026-09-24T17:17:08.723

Modified: 2026-09-24T17:17:08.853

Link: CVE-2026-91132

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-24T19:45:17Z

Weaknesses