Lightbox & Modal Popup WordPress Plugin <= 2.8.7 — Unauthenticated Stored DOM-Based Cross-Site Scripting via Image Alt Attribute in .wp-caption Containers

Overview

Advisory ID

CVE-2026-120687

Product

Lightbox & Modal Popup WordPress Plugin – FooBox foobox-image-lightbox

Affected

≤2.8.7

Fixed in

2.8.8

Weakness

CWE-79 Cross-Site Scripting

Required access

No account needed

Published

Nov 14, 2026

Credit

Adrien Brunner

Source

Wordfence Intelligence

The Lightbox & Modal Popup WordPress Plugin – FooBox plugin for WordPress is vulnerable to Stored DOM-Based Cross-Site Scripting via the 'img alt attribute inside .wp-caption container' parameter in all versions up to, and including, 2.8.7 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This is exploitable by Subscriber-level users when bbPress is installed, as its bbp_filter_kses filter chain permits img and pre tags while preserving numeric character references inside attribute values, allowing encoded payloads to bypass save-time sanitization and reach the vulnerable sink fully intact. Exploitation by attackers with subscriber-level access and above requires that bbPress 2.6.20 is installed, a public forum exists, and either the first topic has already been approved or subsequent topics clear moderation. On a default installation, where that is not configured, the vulnerability requires attackers with contributor-level access and above.

Not sure which version you run? Run a passive check — it reads public files only.

Remediation & mitigations

1. Update to version 2.8.8, or a newer patched version
2. Rotate administrator passwords and application secrets if the site ran a vulnerable version while publicly reachable.