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CVE-2026-91122— Discourse: Chat MessageBus delivers read-restricted messages to unauthorized users

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 是一个开源的讨论平台。在版本 2026.1.8、2026.6.3、2026.7.2 和 2026.8.0 之前，其视频占位符组件允许通过构造的 HTML 实现属性溢出（attribute breakout），从而注入攻击者可控的事件处理程序。具备默认信任级别发帖权限的已认证用户可以将该构造好的占位符存储于帖子中。当其他用户打开该帖子并点击视频播放覆盖层时，该事件处理程序便可在查看者的会话中执行任意 JavaScript 代码。尽管默认的内容安全策略（CSP）设置会阻止内联事件处理程序，但在 CS

CVSS 8.7 · High EPSS 0.26% · P16
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I. Basic Information for CVE-2026-91122

Vulnerability Information
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Vulnerability Title
Discourse: Chat MessageBus delivers read-restricted messages to unauthorized users
Source: CVE Program / CVE List V5
Vulnerability Description
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the video placeholder component allowed crafted HTML to cause an attribute breakout and inject an attacker-controlled event handler. An authenticated user with default trust-level posting privileges could store the crafted placeholder in a post. When another user opened the post and clicked the video play overlay, the handler could execute arbitrary JavaScript in the viewer's session. Default Content Security Policy settings block inline event handlers, but instances with CSP disabled or relaxed could allow the script to read page content and make authenticated requests as the viewer. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
discourse discourse < 2026.8.0 -

II. Public POCs for CVE-2026-91122

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III. Intelligence Information for CVE-2026-91122

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Other References for CVE-2026-91122 (6)

Same Patch Batch · discourse · 2026-09-24 · 9 CVEs total

CVE-2026-91123 7.2 HIGH Discourse: Reject literal backslash path separators in iframe src traversal guard
CVE-2026-91133 6.5 MEDIUM Discourse: Escape LIKE metacharacters in upload paths to prevent disclosure
CVE-2026-91119 6.4 MEDIUM Discourse: Encode action_code_who in mention URLs
CVE-2026-91134 5.4 MEDIUM Discourse: Block post iframes whose encoded userinfo bypasses the allowed_iframes allowlis
CVE-2026-91120 5.4 MEDIUM Discourse: Stored HTML injection in video notification emails
CVE-2026-91121 5.0 MEDIUM Discourse: Chat upload filenames rendered as raw HTML in excerpts
CVE-2026-91132 4.3 MEDIUM Discourse: Wildcard iframe origin allowlist bypass via authority separators
CVE-2026-84302 4.2 MEDIUM Discourse: Non-participant moderators can read, edit, and delete PM content through Discou

IV. Related Vulnerabilities

Same product: discourse
Same vendor: discourse
Same weakness: CWE-79

V. Comments for CVE-2026-91122

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