CVE-2025-0769: PixelYourSite Plugin RCE Vulnerability

CVE-2025-0769 Overview

CVE-2025-0769 is an insecure deserialization vulnerability [CWE-502] in the PixelYourSite WordPress plugin, version 10.1.1.1. The flaw exists in myapp/modules/facebook/facebook-server-async-task.php, where unvalidated user input is passed directly to a PHP unserialize() function. An attacker can supply crafted serialized data over the network without authentication, potentially triggering PHP object injection during deserialization. The vulnerability was disclosed through a Fluid Attacks security advisory.

Critical Impact
Unauthenticated attackers can send crafted serialized payloads to trigger PHP object injection, which can lead to limited integrity and availability impact on affected WordPress sites running the plugin.

Affected Products

PixelYourSite - Your smart PIXEL (TAG) and API Manager plugin for WordPress
Version 10.1.1.1
Vulnerable file: myapp/modules/facebook/facebook-server-async-task.php

Discovery Timeline

2025-02-28 - CVE-2025-0769 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-0769

Vulnerability Analysis

The PixelYourSite plugin processes asynchronous Facebook server-side task requests through the facebook-server-async-task.php handler. The handler consumes user-supplied input and passes it directly to PHP's unserialize() function without validation or sanitization. This pattern is a well-known insecure deserialization defect classified under [CWE-502].

When unserialize() reconstructs a PHP object from attacker-controlled data, any magic methods such as __wakeup() or __destruct() on classes present in the WordPress runtime can be invoked. If a suitable POP (property-oriented programming) gadget chain exists in loaded plugins or themes, this behavior can be chained to file operations, SQL statements, or other sensitive functions.

The attack requires no authentication and is deliverable remotely over the network. Attack complexity is elevated because exploitation typically depends on the availability of usable gadget chains within the target's PHP environment.

Root Cause

The root cause is the direct use of unserialize() on untrusted input inside the Facebook server-side async task module. PHP's native deserialization mechanism instantiates arbitrary objects and executes their lifecycle methods, making it unsafe for handling any data derived from HTTP requests without strict allowlists or the use of safer formats such as JSON.

Attack Vector

An unauthenticated remote attacker submits an HTTP request to the endpoint serviced by facebook-server-async-task.php, embedding a serialized PHP object payload in the parameter processed by unserialize(). When the plugin deserializes the payload, gadget chains in loaded WordPress components may execute, resulting in unauthorized modification of data or denial of service on the affected site.

The vulnerability manifests in the Facebook async task handler. See the Fluid Attacks Security Advisory for additional technical detail.

Detection Methods for CVE-2025-0769

Indicators of Compromise

HTTP requests to /wp-content/plugins/pixelyoursite/myapp/modules/facebook/facebook-server-async-task.php containing serialized PHP payloads recognizable by prefixes such as O:, a:, or s: followed by length and type markers.
Unexpected PHP errors or warnings in web server logs referencing unserialize(), __wakeup, or __destruct originating from the PixelYourSite plugin path.
Anomalous file writes, outbound network connections, or database modifications originating from the PHP worker process shortly after requests to the async task endpoint.

Detection Strategies

Deploy web application firewall (WAF) rules that inspect POST bodies and query parameters for PHP serialization patterns targeting the plugin path.
Enable PHP error and access logging, then correlate unserialize() warnings with source IP addresses to identify probing activity.
Perform plugin inventory across WordPress deployments to identify any host running PixelYourSite 10.1.1.1 or earlier.

Monitoring Recommendations

Monitor WordPress plugin directories for file integrity changes and new PHP files placed by post-exploitation activity.
Alert on outbound connections from PHP-FPM or Apache worker processes to unexpected destinations following requests to plugin async endpoints.
Track authentication anomalies and privileged WordPress account creation that could indicate successful exploitation.

How to Mitigate CVE-2025-0769

Immediate Actions Required

Upgrade the PixelYourSite plugin to a version later than 10.1.1.1 that addresses the deserialization defect. Consult the PixelYourSite Plugin page for the latest release.
If a patched version is not yet deployable, deactivate and remove the PixelYourSite plugin from affected WordPress sites.
Review web server and application logs for prior exploitation attempts against facebook-server-async-task.php.

Patch Information

Vendor patch information is available through the WordPress plugin repository. Site operators should update to the current PixelYourSite release, which addresses the unsafe unserialize() call in the Facebook async task handler. Verify the plugin version after update by inspecting the plugin metadata in the WordPress admin console.

Workarounds

Block or restrict access to /wp-content/plugins/pixelyoursite/myapp/modules/facebook/facebook-server-async-task.php at the web server or WAF layer until patched.
Add WAF signatures that reject request bodies containing PHP serialization markers such as O:<digits>:" targeting the plugin endpoint.
Run PHP with the phar.readonly=1 directive and disable unnecessary classes to reduce the pool of available deserialization gadgets.

bash

# Nginx example: deny direct access to the vulnerable endpoint
location ~* /wp-content/plugins/pixelyoursite/myapp/modules/facebook/facebook-server-async-task\.php$ {
    deny all;
    return 403;
}