CVE-2025-39358: WP Posts Carousel Object Injection Flaw

CVE-2025-39358 Overview

CVE-2025-39358 is a PHP Object Injection vulnerability in the teastudio.pl WP Posts Carousel WordPress plugin. The flaw is caused by deserialization of untrusted data [CWE-502] in wp-posts-carousel versions up to and including 1.3.12. An authenticated attacker with low privileges can submit crafted serialized payloads that the plugin unserializes, leading to object injection. When suitable PHP magic methods or gadget chains are present in the WordPress environment, this can escalate to arbitrary code execution, file manipulation, or data exfiltration.

Critical Impact
Successful exploitation allows authenticated attackers to inject PHP objects into the application, potentially resulting in remote code execution, full site compromise, and loss of confidentiality, integrity, and availability.

Affected Products

teastudio.pl WP Posts Carousel plugin for WordPress
All versions from n/a through <= 1.3.12
WordPress sites with the wp-posts-carousel plugin installed and active

Discovery Timeline

2025-06-06 - CVE-2025-39358 published to NVD
2026-04-29 - Last updated in NVD database

Technical Details for CVE-2025-39358

Vulnerability Analysis

The vulnerability stems from unsafe deserialization of attacker-controlled input within the wp-posts-carousel plugin. PHP's unserialize() function reconstructs objects from serialized strings. When that input is reachable by a low-privileged user, an attacker can supply a crafted payload that instantiates arbitrary classes loaded in the WordPress runtime.

Object injection by itself does not always execute code. The real impact depends on available gadget chains in WordPress core, other installed plugins, or themes. WordPress environments commonly contain classes with __destruct, __wakeup, or __toString methods that can be abused to read files, write to disk, or execute commands. The vulnerability is tracked under CWE-502: Deserialization of Untrusted Data and carries an EPSS probability of 0.336%.

Root Cause

The plugin passes user-supplied data to a PHP deserialization routine without first validating or restricting the resulting class types. Because the input crosses a trust boundary without sanitization, attackers control the structure and class names of the resulting objects.

Attack Vector

The attack vector is network-based and requires only low privileges, with no user interaction. An authenticated user submits a serialized PHP object through a plugin parameter or stored field. The plugin unserializes the payload, triggering magic methods on attacker-chosen classes and activating gadget chains for code execution or data tampering.

// Vulnerability mechanism (conceptual, no verified PoC available)
// Attacker-supplied serialized payload reaches an unserialize() call
// within the wp-posts-carousel plugin. See the Patchstack advisory
// for technical details: https://patchstack.com/database/Wordpress/Plugin/wp-posts-carousel

Detection Methods for CVE-2025-39358

Indicators of Compromise

HTTP POST requests to wp-admin endpoints containing serialized PHP markers such as O:, a:, or s: in parameter values associated with the WP Posts Carousel plugin.
Unexpected PHP files written under wp-content/uploads/ or modifications to plugin or theme files following requests to wp-posts-carousel routes.
New or modified WordPress administrator accounts created shortly after suspicious requests to plugin endpoints.
Outbound network connections initiated by the PHP worker process to unknown hosts following plugin interactions.

Detection Strategies

Inspect web server and WordPress request logs for serialized object signatures in parameters handled by wp-posts-carousel.
Monitor file integrity across wp-content/plugins/, wp-content/themes/, and the WordPress root for unexpected changes.
Correlate authenticated user activity with subsequent PHP process spawning of shell utilities such as sh, bash, curl, or wget.

Monitoring Recommendations

Enable PHP error and access logging for the WordPress host and forward logs to a centralized analytics platform.
Alert on web application firewall signatures matching PHP object injection patterns targeting WordPress plugins.
Track plugin version inventory across WordPress sites and flag any instance running wp-posts-carousel at version 1.3.12 or earlier.

How to Mitigate CVE-2025-39358

Immediate Actions Required

Identify every WordPress instance running the wp-posts-carousel plugin and confirm the installed version.
Update the plugin to a fixed release once published by the vendor, or deactivate and remove it until a patch is available.
Rotate WordPress administrator credentials and review user accounts for unauthorized additions after exposure.
Audit wp-content/ directories for unexpected files and revert any unauthorized changes from backup.

Patch Information

The vulnerability affects WP Posts Carousel through version 1.3.12. Refer to the Patchstack Vulnerability Report for the current fix status and vendor advisory updates. Apply the patched release as soon as it becomes available on the WordPress plugin repository.

Workarounds

Deactivate and remove the wp-posts-carousel plugin until a vendor patch is installed.
Restrict access to authenticated WordPress roles capable of reaching the vulnerable plugin functionality, limiting exposure to trusted users only.
Deploy a web application firewall rule that blocks serialized PHP object patterns in requests targeting plugin endpoints.
Enforce least privilege on the PHP-FPM or web server user to limit the impact of any successful object injection.

bash

# Temporary mitigation: disable the vulnerable plugin via WP-CLI
wp plugin deactivate wp-posts-carousel
wp plugin delete wp-posts-carousel