{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-27166", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-02-18T00:18:53.962Z", "datePublished": "2026-03-19T20:29:22.570Z", "dateUpdated": "2026-03-21T03:31:58.296Z"}, "containers": {"cna": {"title": "Discourse vulnerable to HTML injection via prohibited iframe URLs", "problemTypes": [{"descriptions": [{"cweId": "CWE-80", "lang": "en", "description": "CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 4.1, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "LOW", "scope": "CHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N", "version": "3.1"}}], "references": [{"name": "https://github.com/discourse/discourse/security/advisories/GHSA-h653-cq78-vjj2", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/discourse/discourse/security/advisories/GHSA-h653-cq78-vjj2"}, {"name": "https://github.com/discourse/discourse/commit/c4762a4fac2f61f52f325396b11d3aeb955ea925", "tags": ["x_refsource_MISC"], "url": "https://github.com/discourse/discourse/commit/c4762a4fac2f61f52f325396b11d3aeb955ea925"}], "affected": [{"vendor": "discourse", "product": "discourse", "versions": [{"version": "< 2026.3.0-latest.1", "status": "affected"}, {"version": ">= 2026.2.0-latest, < 2026.2.1", "status": "affected"}, {"version": ">= 2026.1.0-latest, < 2026.1.2", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-03-19T20:29:22.570Z"}, "descriptions": [{"lang": "en", "value": "Discourse is an open source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2, insufficient cleanup in the default Codepen allowed iframes value allows an attacker to trick a user into changing the URL of the main page. This issue has been fixed in versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2. To workaround this issue, remove Codepen from the list of allowed iframes."}], "source": {"advisory": "GHSA-h653-cq78-vjj2", "discovery": "UNKNOWN"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-03-21T03:31:46.439342Z", "id": "CVE-2026-27166", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-03-21T03:31:58.296Z"}}]}}

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{"configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*", "matchCriteriaId": "0B441F8E-6577-4447-B9B4-767A925FAD77", "versionEndExcluding": "2026.3.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*", "matchCriteriaId": "4BE96625-3609-410C-B41E-4A824C1A57C0", "versionEndExcluding": "2026.1.2", "versionStartIncluding": "2026.1.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*", "matchCriteriaId": "FD31CF04-CF2F-4FB9-8880-9243BC7671A7", "versionEndExcluding": "2026.2.1", "versionStartIncluding": "2026.2.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:discourse:discourse:2026.3.0:*:*:*:latest:*:*:*", "matchCriteriaId": "E3FE9277-4F6B-4FD0-991F-F0FB8D226E1C", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Discourse is an open source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2, insufficient cleanup in the default Codepen allowed iframes value allows an attacker to trick a user into changing the URL of the main page. This issue has been fixed in versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2. To workaround this issue, remove Codepen from the list of allowed iframes."}, {"lang": "es", "value": "Discourse es una plataforma de discusi\u00f3n de c\u00f3digo abierto. Antes de las versiones 2026.3.0-latest.1, 2026.2.1 y 2026.1.2, una limpieza insuficiente en el valor predeterminado de iframes permitidos de Codepen permite a un atacante enga\u00f1ar a un usuario para que cambie la URL de la p\u00e1gina principal. Este problema ha sido solucionado en las versiones 2026.3.0-latest.1, 2026.2.1 y 2026.1.2. Como soluci\u00f3n alternativa a este problema, elimine Codepen de la lista de iframes permitidos."}], "id": "CVE-2026-27166", "lastModified": "2026-03-25T01:06:00.000", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 4.1, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "LOW", "scope": "CHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 2.3, "impactScore": 1.4, "source": "security-advisories@github.com", "type": "Secondary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 5.4, "baseSeverity": "MEDIUM", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "privilegesRequired": "LOW", "scope": "CHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 2.3, "impactScore": 2.7, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2026-03-19T21:17:08.740", "references": [{"source": "security-advisories@github.com", "tags": ["Patch"], "url": "https://github.com/discourse/discourse/commit/c4762a4fac2f61f52f325396b11d3aeb955ea925"}, {"source": "security-advisories@github.com", "tags": ["Vendor Advisory"], "url": "https://github.com/discourse/discourse/security/advisories/GHSA-h653-cq78-vjj2"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-80"}], "source": "security-advisories@github.com", "type": "Primary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,2026.3.0-latest.1)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[2026.2.0-latest,2026.2.1)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[2026.1.0-latest,2026.1.2)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "discourse", "source": "cna", "vendor": "discourse"}, "product": "discourse", "vendor": "discourse"}], "analysis": {"en": {"generated_at": "2026-03-25T03:04:22.489361+00:00", "value": {"mitigation_remediation": ["Upgrade Discourse to version 2026.3.0-latest.1, 2026.2.1, or 2026.1.2 to apply the official fix.", "If an upgrade is not immediately possible, edit the allowed iframes list in the configuration and remove Codepen entries to block the vulnerable embeds."], "summary": {"action": "Patch", "impact": "HTML injection that can redirect a user\u2019s browser to a malicious URL"}, "threat_synthesis": {"affected_systems": "Discourse is affected for all releases prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2. Users running those versions should verify their current build and apply updates accordingly.", "description_and_impact": "The vulnerability originates from insufficient sanitization of URLs allowed in the default Codepen iframe configuration. An attacker can craft content that, when viewed by a user, injects HTML into the page and tricks the browser into navigating to a different URL. This can enable phishing or social engineering attacks against users, but does not provide arbitrary code execution on the server.", "risk_and_exploitability": "The CVSS score of 4.1 indicates moderate severity, while the EPSS score of less than 1% shows a low likelihood of widespread exploitation at present. The vulnerability relies on a user viewing malicious content; no special privileges are needed. Native mitigations from Discourse are not listed in the CISA KEV catalog, reinforcing the need for a patch or configuration change."}}}}, "created": "2026-03-20T08:56:16.362546+00:00", "updated": "2026-03-25T11:55:02.962658+00:00", "vendors": ["discourse", "discourse$PRODUCT$discourse"]}