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CVE-2026-27166— Discourse vulnerable to HTML injection via prohibited iframe URLs

Quick assessment

Affected
discourse discourse
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Discourse是Discourse开源的一套开源的社区讨论平台。该平台包括社区、电子邮件和聊天室等功能。 Discourse 2026.3.0-latest.1之前版本、2026.2.1之前版本和2026.1.2之前版本存在安全漏洞，该漏洞源于默认Codepen允许的iframe值清理不足，可能导致攻击者诱骗用户更改主页URL。

CVSS 4.1 · Medium EPSS 0.26% · P16
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I. Basic Information for CVE-2026-27166

Vulnerability Information
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Vulnerability Title
Discourse vulnerable to HTML injection via prohibited iframe URLs
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
Web页面中脚本相关HTML标签转义处理不恰当(基本跨站脚本)
Source: CVE Program / CVE List V5
Vulnerability Title
Discourse 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Discourse是Discourse开源的一套开源的社区讨论平台。该平台包括社区、电子邮件和聊天室等功能。 Discourse 2026.3.0-latest.1之前版本、2026.2.1之前版本和2026.1.2之前版本存在安全漏洞，该漏洞源于默认Codepen允许的iframe值清理不足，可能导致攻击者诱骗用户更改主页URL。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
discourse discourse < 2026.3.0-latest.1 -

II. Public POCs for CVE-2026-27166

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III. Intelligence Information for CVE-2026-27166

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Patches & Fixes for CVE-2026-27166 (1)

Vendor Advisories for CVE-2026-27166 (1)

Same Patch Batch · discourse · 2026-03-19 · 17 CVEs total

CVE-2026-33355 6.5 MEDIUM Discourse filters whisper posts from private-posts feed
CVE-2026-33410 5.4 MEDIUM Discourse hardens chat DM channel creation and expansion
CVE-2026-27454 5.3 MEDIUM Discourse has check revision visibility on posts endpoint
CVE-2026-33395 4.4 MEDIUM Discourse has stored click‑based XSS via Graphviz SVG javascript: links
CVE-2026-32099 4.3 MEDIUM Discourse prevents hidden profile data leak via user onebox
CVE-2026-33393 4.3 MEDIUM Discourse fixes loose hostname matching in spam host allowlist
CVE-2026-33394 2.7 LOW Discourse leaks PM post edits to moderators
CVE-2026-33408 2.2 LOW Discourse has Improper Authorization in "Post Edits" Report For Moderators
CVE-2026-27491 Discourse has a bypass of official warnings messages by non-staff users
CVE-2026-27570 Discourse Vulnerable to Stored XSS via Shared AI Conversation Onebox
CVE-2026-27740 Discourse has Stored XSS in AI Triage Automation
CVE-2026-27934 Discourse leaks private topic title and post excerpt via user action API endpoint
CVE-2026-27935 Discourse leaks private topic metadata to non-authorized users
CVE-2026-27936 Discourse discloses restricted post-action counts to non-privileged users
CVE-2026-28282 Discourse vulnerable to group membership addition permission bypass via discourse-policy p
CVE-2026-29072 Discourse missing permission check for policy creation in discourse-policy

IV. Related Vulnerabilities

Same product: discourse
Same vendor: discourse
Same weakness: CWE-80

V. Comments for CVE-2026-27166

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