CVE-2026-91119 (GCVE-0-2026-91119)
Vulnerability from cvelistv5 – Published: 2026-09-24 17:07 – Updated: 2026-09-28 15:00
VLAI
EPSS
VEX
Title
Discourse: Encode action_code_who in mention URLs
Summary
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.
Severity
6.4 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-28 14:59 UTC
CWE
- CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Assigner
References
6 references
| URL | Tags |
|---|---|
| https://github.com/discourse/discourse/security/a… | x_refsource_CONFIRM |
| https://github.com/discourse/discourse/pull/42882 | x_refsource_MISC |
| https://github.com/discourse/discourse/commit/20d… | x_refsource_MISC |
| https://github.com/discourse/discourse/commit/666… | x_refsource_MISC |
| https://github.com/discourse/discourse/commit/77a… | x_refsource_MISC |
| https://github.com/discourse/discourse/commit/c47… | x_refsource_MISC |
Impacted products
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"version": "\u003c 2026.8.0"
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"version": "\u003e= 2026.7.0-latest, \u003c 2026.7.2"
},
{
"status": "affected",
"version": "\u003e= 2026.6.0-latest, \u003c 2026.6.3"
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}
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"scope": "CHANGED",
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{
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"tags": [
"x_refsource_MISC"
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"url": "https://github.com/discourse/discourse/commit/77a81c7a3a7ff9e94b355e32b8f379f2d389e05a"
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{
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"version": "\u003e= 2026.6.0-latest, \u003c 2026.6.3"
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"version": "\u003e= 2026.1.0-latest, \u003c 2026.1.8"
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"lastModified": "2026-09-28T16:17:16.950",
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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