CVE-2026-3347 in Multi Functional Flexi Lightbox Plugin
Summary
by MITRE • 03/21/2026
The Multi Functional Flexi Lightbox plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the `arv_lb[message]` parameter in all versions up to, and including, 1.2 due to insufficient input sanitization and output escaping. This is due to the `arv_lb_options_val()` sanitize callback returning user input without any sanitization, and the stored `message` value being output in the `genLB()` function without escaping. This makes it possible for authenticated attackers, with Administrator-level access, to inject arbitrary web scripts in pages that will execute whenever a user accesses a page or post with the lightbox enabled.
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Analysis
by VulDB Data Team • 03/21/2026
The vulnerability identified as CVE-2026-3347 affects the Multi Functional Flexi Lightbox WordPress plugin, presenting a critical stored cross-site scripting flaw that enables authenticated attackers with administrator privileges to execute malicious scripts within user browsers. This vulnerability exists in all plugin versions up to and including 1.2, making it a widespread concern for WordPress installations utilizing this specific plugin. The flaw stems from inadequate input validation and output escaping mechanisms within the plugin's codebase, creating a persistent security risk that can compromise user sessions and potentially lead to full system compromise.
The technical implementation of this vulnerability occurs through the `arv_lb[message]` parameter which serves as the attack vector for the stored XSS exploit. The plugin's `arv_lb_options_val()` sanitize callback function fails to properly process user input, instead returning the raw user-supplied data without any sanitization measures. This unfiltered input then gets stored in the database and subsequently retrieved by the `genLB()` function during page rendering. The critical oversight lies in the lack of proper output escaping when the stored message value is rendered in the lightbox functionality, allowing malicious JavaScript code to persist and execute whenever users view pages containing the affected lightbox component. This vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws due to insufficient input sanitization and output escaping.
The operational impact of this vulnerability is significant for WordPress administrators and end-users who rely on the Multi Functional Flexi Lightbox plugin for content presentation. Authenticated attackers with administrator-level access can inject malicious scripts that execute in the context of other users' browsers, potentially leading to session hijacking, data theft, or privilege escalation attacks. The stored nature of this XSS vulnerability means that once the malicious payload is injected, it will persist and execute automatically whenever affected pages are accessed, making it particularly dangerous for high-traffic websites or those with numerous administrators. This vulnerability can be exploited to create backdoors, steal cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users within the WordPress environment.
Mitigation strategies for this vulnerability should prioritize immediate plugin updates to versions that address the sanitization and escaping issues. System administrators must ensure that all WordPress installations using this plugin are updated to the latest available version that contains proper input validation and output escaping mechanisms. Additionally, implementing proper access controls and monitoring for unusual administrative activities can help detect potential exploitation attempts. The remediation approach should include thorough code review of the plugin's sanitize callbacks and output escaping functions to ensure that all user-provided data is properly validated before storage and appropriately escaped before rendering. Organizations should also consider implementing web application firewalls and content security policies as additional protective measures to prevent exploitation of similar vulnerabilities in other plugins or components. This vulnerability demonstrates the importance of proper input validation and output escaping practices in web applications, as outlined in the OWASP Top Ten and ATT&CK framework's web application exploitation techniques.