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Back to active CVEs
High · CVSS 7.7CVE-2026-91159

Discourse: Stored oEmbed HTML injection via allowed iframeCVE-2026-91159

Answer in brief

CVE-2026-91159 records a High severity (CVSS 7.7) vulnerability in Discourse: Stored oEmbed HTML injection via allowed iframe. The current sources do not mark it as known exploited. The current feed maps discourse/discourse (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 14, 2026Updated Oct 14, 2026Source checked Oct 14, 2026First seen by HOL Oct 14, 2026Material review Oct 14, 2026
Upstream Advisory

Key facts

Risk
High · CVSS 7.7
Exploitation
Not marked as known exploited
Affected software
1 mapped package or product
Fix availability
Available

Why this deserves its current priority

CVSS is 7.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps discourse/discourse (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
discourse/discoursegeneric<2026.1.9 || >=2026.7.0-latest <2026.7.3 || >=2026.8.0-latest <2026.8.1 || >=2026.9.0-latest <2026.9.02026.1.9, 2026.7.3, 2026.8.1, 2026.9.0

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for discourse/discourse.
  2. 2Review the reported fix. Update discourse/discourse to 2026.1.9 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    Oct 14, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Oct 14, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Oct 14, 2026

Sources and claim methodology

  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
Upstream source description

Discourse is an open-source discussion platform. Prior to 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9, oEmbed processing treated an entire attacker-controlled HTML fragment as trusted when the fragment contained an iframe whose source matched the configured allowlist. A user with posting permission who controlled a public webpage and its oEmbed response could combine an allowlisted iframe with unrelated sibling HTML or CSS, causing stored visual overlays or other styled content to appear in post content and enabling misleading or fraudulent user interfaces. Exploitation requires a posting account, control of the fetched webpage and oEmbed response, and an allowlisted iframe source. The issue affects content integrity but does not expose restricted data, disrupt availability, or require interaction with Discourse Content Security Policy. This issue is fixed in versions 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9.

Quoted source text, attributed separately from HOL analysis.

Related CVEs

  • Dpdk: dpdk: heap out-of-bounds read/write in gso header copySame generic ecosystem
  • Junos OS and Junos OS Evolved: An unprivileged local attacker causes denial of service or privilege escalationSame generic ecosystem
  • Junos OS and Junos OS Evolved: An attacker causes Denial of Service in eventdSame generic ecosystem
  • Junos OS: SRX Series: An attacker causes data-plane denial of service when chassis-cluster high availability is enabledSame generic ecosystem
  • Junos OS: SRX Series: An attacker causes data-plane denial of service when chassis-cluster high availability is usedSame generic ecosystem
  • Junos OS and Junos OS Evolved: SRX Series: An attacker causes a forwarding-plane outage when SVR vector routing is usedSame generic ecosystem

Record context

Vulnerability class
XSS
EPSS
Not reported
CWE IDs
CWE-79
Source
CVE List V5
Source checked
Oct 14, 2026
References
5 linked sources
Open source record