Discourse: Encode action_code_who in mention URLs (CVE-2026-91119) | HOL Guard CVE

Medium · CVSS 6.4CVE-2026-91119

Discourse: Encode action_code_who in mention URLs

Answer in brief

CVE-2026-91119 records a Medium severity (CVSS 6.4) vulnerability in Discourse: Encode action_code_who in mention URLs. 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 Sep 24, 2026Updated Sep 24, 2026Source checked Sep 25, 2026First seen by HOL Sep 25, 2026Material review Sep 24, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.4
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 6.4. 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
Package	Affected range	Fixed version
discourse/discoursegeneric	<2026.8.0 \|\| >=2026.7.0-latest <2026.7.2 \|\| >=2026.6.0-latest <2026.6.3 \|\| >=2026.1.0-latest <2026.1.8	2026.8.0, 2026.7.2, 2026.6.3, 2026.1.8

Recommended response

Check inventory. Check lockfiles and deployed manifests for discourse/discourse.
Review the reported fix. Update discourse/discourse to 2026.8.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 25, 2026

Sources and claim methodology

Upstream source description

Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the topic small-action and nested-activity-log components interpolated the free-form action_code_who value into mention-link href attributes without URL encoding. A quote-bearing display name could terminate the intended URL attribute and inject attacker-controlled elements into the trusted rendered markup. Although the visible mention text was escaped, the unencoded path component allowed stored HTML injection when another user viewed the affected topic action or activity log. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

Quoted source text, attributed separately from HOL analysis.