CVE-2025-49855: Meks Flexible Shortcodes XSS Vulnerability

CVE-2025-49855 Overview

CVE-2025-49855 is a DOM-based Cross-Site Scripting (XSS) vulnerability in the Meks Flexible Shortcodes plugin for WordPress. The flaw affects all plugin versions up to and including 1.3.7. It stems from improper neutralization of user input during web page generation, classified as [CWE-79].

Attackers with low privileges can inject malicious scripts that execute in the browser of any user who interacts with a crafted link or page. Successful exploitation requires user interaction and can lead to session compromise, credential theft, or unauthorized actions within the WordPress site context.

Critical Impact
Authenticated attackers can execute arbitrary JavaScript in victim browsers, enabling session hijacking and unauthorized actions on WordPress sites running the vulnerable plugin.

Affected Products

Meks Flexible Shortcodes plugin for WordPress
All versions from n/a through 1.3.7
WordPress sites with the plugin installed and active

Discovery Timeline

2025-06-17 - CVE-2025-49855 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-49855

Vulnerability Analysis

The vulnerability is a DOM-based XSS flaw [CWE-79] in the Meks Flexible Shortcodes WordPress plugin. DOM-based XSS occurs when client-side JavaScript writes attacker-controlled data into the Document Object Model (DOM) without proper sanitization or encoding.

Unlike reflected or stored XSS, the payload never needs to touch the server-side response. The malicious script executes entirely within the victim's browser when vulnerable JavaScript processes attacker-supplied values. This makes the issue harder to detect using traditional server-side logging.

Exploitation requires an authenticated user with low privileges and some form of user interaction. The scope change in this issue means the vulnerability can affect resources beyond the vulnerable component, such as other browser contexts or site content.

Root Cause

The plugin's client-side code fails to properly neutralize input before writing it to the DOM. Values that reach sinks such as innerHTML, document.write, or eval are not escaped or sanitized. This allows script content embedded in shortcode parameters or related inputs to execute in the browser.

Attack Vector

An attacker with low-level WordPress credentials crafts a shortcode or URL containing a JavaScript payload. When another user—including a site administrator—loads a page that processes the malicious input, the script runs in the victim's browser session. The attacker can steal cookies, perform actions on behalf of the victim, or redirect the user to attacker-controlled infrastructure. See the Patchstack XSS Vulnerability Report for additional technical details.

Detection Methods for CVE-2025-49855

Indicators of Compromise

Unexpected <script> tags or JavaScript event handlers in shortcode parameters stored in the WordPress database.
Unusual outbound requests from administrator browsers to unfamiliar domains after viewing content containing shortcodes.
New or modified administrator accounts created shortly after a privileged user accessed a page with user-generated shortcodes.

Detection Strategies

Audit WordPress wp_posts and wp_postmeta tables for shortcode attributes containing script tags, javascript: URIs, or encoded payloads.
Monitor web server access logs for requests containing suspicious query parameters that could trigger DOM-based execution.
Deploy Content Security Policy (CSP) violation reporting to identify unexpected inline script execution attempts.

Monitoring Recommendations

Enable WordPress audit logging to track changes to posts and shortcode content by low-privilege users.
Review browser-side telemetry and error reports for anomalous DOM manipulation events on pages using the plugin.
Alert on administrator session activity originating from unexpected IP addresses or user agents.

How to Mitigate CVE-2025-49855

Immediate Actions Required

Identify all WordPress installations running Meks Flexible Shortcodes version 1.3.7 or earlier.
Restrict contributor and author-level accounts from using the plugin's shortcodes until a patch is applied.
Review existing posts and pages for malicious shortcode content and remove any suspicious entries.

Patch Information

At the time of publication, no fixed version is listed in the available advisory data. Administrators should monitor the Patchstack XSS Vulnerability Report and the official plugin repository for a release addressing CVE-2025-49855. Apply the patched version as soon as it becomes available.

Workarounds

Deactivate and remove the Meks Flexible Shortcodes plugin until a patched version is released.
Implement a strict Content Security Policy that blocks inline scripts and limits allowed script sources.
Deploy a Web Application Firewall (WAF) rule to filter shortcode parameters containing script-like payloads.
Reduce the number of accounts with post-editing privileges to limit the pool of potential attackers.

bash

# Configuration example: deactivate the plugin via WP-CLI
wp plugin deactivate meks-flexible-shortcodes
wp plugin delete meks-flexible-shortcodes