CVE-2026-118438 in Lightbox Plugin
Summary
by MITRE • 10/31/2026
The Firelight Lightbox WordPress plugin before 2.3.24 does not properly escape image attribute values before processing them in the browser, which could allow users with contributor-level access and above to inject arbitrary web scripts that execute when another user views or previews the affected content.
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Analysis
by VulDB Data Team • 10/31/2026
The Firelight Lightbox WordPress plugin version 2.3.24 and earlier contains a critical Cross-Site Scripting vulnerability stemming from insufficient input validation and output encoding mechanisms. This flaw specifically affects how image attribute values are processed within the application's frontend rendering logic. When content containing these attributes is served to end-users, the browser interprets unescaped special characters as executable code rather than static data. The root cause lies in the plugin's failure to properly sanitize or encode user-supplied input before it is embedded into HTML elements, creating a direct pathway for malicious script injection. This type of vulnerability is formally categorized under CWE-79, which defines Improper Neutralization of Input During Web Page Generation as a standard weakness classification for stored and reflected cross-site scripting flaws in web applications.
The operational impact of this vulnerability is significant due to the relatively low privilege level required to exploit it. Attackers with contributor-level access or higher can inject arbitrary JavaScript payloads into image attributes associated with posts, pages, or media items within the WordPress environment. Unlike administrative vulnerabilities that require full site control, this flaw allows lower-privileged users to execute code in the context of other users who view or preview the compromised content. When a victim user loads the affected page, their browser executes the injected scripts, potentially leading to session hijacking through cookie theft, credential harvesting via keyloggers, defacement of the visual interface, or redirection to malicious third-party sites designed for phishing attacks. The persistence of this threat is heightened because stored XSS payloads remain active until the vulnerable content is manually edited and saved with proper sanitization by an administrator.
From a tactical perspective, this vulnerability aligns closely with MITRE ATT&CK technique T1059, which covers Command and Scripting Interpreter execution within browser environments. The attacker leverages the trusted relationship between the victim's session and the WordPress application to bypass same-origin policy restrictions implicitly granted by the browser when loading content from the site domain. This enables the exfiltration of sensitive data such as authentication tokens, personal information stored in local storage, or administrative credentials if multi-factor authentication is not enforced. The ability for contributors to execute scripts means that any user with editorial rights can compromise the security posture of other users without needing elevated privileges, effectively widening the attack surface beyond what traditional role-based access controls might anticipate.
Mitigation strategies must address both immediate remediation and long-term defensive coding practices. The primary solution is to upgrade the Firelight Lightbox plugin to version 2.3.24 or later, where developers have implemented proper output encoding for image attributes using context-aware escaping functions provided by the WordPress framework. For organizations unable to update immediately due to compatibility constraints, temporary workarounds include restricting contributor-level access until patches are applied and manually auditing existing media items for suspicious attribute values. Security teams should also enforce Content Security Policy headers that restrict script execution sources where feasible, although this is not a substitute for fixing the underlying input validation flaw. Regular security audits focusing on user-input handling in frontend rendering components will help prevent similar vulnerabilities from being introduced during future development cycles or plugin updates.