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CVE-2026-72721— Discourse: Onebox Domain Blocklist Bypass via Case-Sensitive Comparison

CVSS 5.3 · Medium

Affected Version Matrix 4

VendorProductVersion RangeStatus
discoursediscourse< 2026.1.6affected
>= 2026.5.0-latest, < 2026.5.2affected
>= 2026.6.0-latest, < 2026.6.1affected
>= 2026.7.0-latest, < 2026.7.0affected
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I. Basic Information for CVE-2026-72721

Vulnerability Information
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Vulnerability Title
Discourse: Onebox Domain Blocklist Bypass via Case-Sensitive Comparison
Source: CVE Program / CVE List V5
Vulnerability Description
Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, Onebox::DomainChecker.is_blocked? compares hostnames and SiteSetting.blocked_onebox_domains entries case-sensitively, allowing an attacker to bypass configured Onebox domain restrictions by changing character casing in a redirect target hostname. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
大小写敏感处理不恰当
Source: CVE Program / CVE List V5

Affected Products

VendorProductAffected VersionsCPESubscribe
discoursediscourse < 2026.1.6 -

II. Public POCs for CVE-2026-72721

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III. Intelligence Information for CVE-2026-72721

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Patches & Fixes for CVE-2026-72721 (8)

Vendor Advisories for CVE-2026-72721 (1)

Same Patch Batch · discourse · 2026-08-10 · 13 CVEs total

CVE-2026-727308.7 HIGHDiscourse: Stored XSS chat-transcript username unescaped in Rich Text Editor
CVE-2026-727317.1 HIGHDiscourse: Strip SQL comments and use non-recursive parameter interpolation in Data Explor
CVE-2026-727266.5 MEDIUMDiscourse: Unauthorized eavesdropping on private AI bot conversations.
CVE-2026-727206.4 MEDIUMDiscourse: HTML injection in PrettyText.format_for_email from cooked-attribute reparsing
CVE-2026-727286.3 MEDIUMDiscourse: Onebox iframe origin allowlist enforces URL authority boundary
CVE-2026-727255.4 MEDIUMDiscourse: Stored XSS in staff action logs injects staff UI
CVE-2026-727235.3 MEDIUMDiscourse: Anonymous sidebar serialization exposes descriptions of category-restricted tag
CVE-2026-727274.8 MEDIUMDiscourse: Stored XSS in the moderation review queue
CVE-2026-727224.3 MEDIUMDiscourse: Duplicate lookup reveals restricted topic titles through canonicalized URLs
CVE-2026-727244.3 MEDIUMDiscourse: Private Chat Threat Message Disclosure via Chat Onebox Channel/Threat ID Mismat
CVE-2026-727324.3 MEDIUMDiscourse: Templates endpoint exposes hidden tag names
CVE-2026-727292.0 LOWDiscourse: Stored XSS in discourse-local-dates plugin

IV. Related Vulnerabilities

Same product: discourse
Same vendor: discourse
Same weakness: CWE-178

V. Comments for CVE-2026-72721

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