CVE-2025-68853: Kleor Contact Manager Object Injection

CVE-2025-68853 Overview

CVE-2025-68853 is a PHP Object Injection vulnerability affecting the Kleor Contact Manager WordPress plugin. The flaw stems from insecure deserialization of untrusted data [CWE-502] in versions up to and including 9.1.1. An attacker can submit a crafted serialized payload that the plugin deserializes, instantiating arbitrary PHP objects within the application context. When suitable gadget chains exist in the WordPress core or other loaded plugins, this primitive can escalate to remote code execution, data tampering, or full site compromise. Exploitation requires network access and minimal user interaction, with no authentication needed.

Critical Impact
Successful exploitation enables object injection that can lead to arbitrary code execution, sensitive data disclosure, and complete compromise of the affected WordPress site.

Affected Products

Kleor Contact Manager WordPress plugin (contact-manager)
All versions from initial release through 9.1.1
WordPress installations with the vulnerable plugin enabled

Discovery Timeline

2026-02-20 - CVE-2025-68853 published to NVD
2026-04-27 - Last updated in NVD database

Technical Details for CVE-2025-68853

Vulnerability Analysis

The vulnerability resides in the Contact Manager plugin's handling of serialized PHP data. The plugin passes attacker-controlled input to unserialize() without validating or restricting the resulting object types. PHP automatically invokes magic methods such as __wakeup(), __destruct(), and __toString() on deserialized objects, which attackers leverage to trigger unintended behavior through gadget chains.

WordPress ecosystems are particularly susceptible because the runtime loads numerous classes from core, themes, and other plugins. Each loaded class expands the gadget surface available to an attacker. A crafted payload that chains together magic methods across these classes can pivot to file writes, database modification, or arbitrary command execution.

The attack requires a single victim interaction, such as visiting a malicious link or page that triggers the vulnerable endpoint. No prior authentication is needed, which broadens the population of viable attackers to any unauthenticated network user.

Root Cause

The root cause is improper input validation before deserialization. The plugin accepts serialized strings from a request channel and feeds them directly into PHP's native unserialize() function. Safer alternatives such as JSON encoding or allow-listing classes through the allowed_classes option were not implemented.

Attack Vector

An unauthenticated attacker delivers a crafted serialized payload to a Contact Manager endpoint accessible over HTTP or HTTPS. The payload is constructed using known gadget chains from WordPress core or co-installed plugins. Upon deserialization, the chain executes attacker-controlled logic in the PHP process running the WordPress site.

For technical details on the vulnerable code path and proof-of-concept conditions, refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2025-68853

Indicators of Compromise

HTTP requests to Contact Manager endpoints containing serialized PHP markers such as O:, a:, or s: in parameters or cookies.
Unexpected PHP error log entries referencing unserialize(), __wakeup, or __destruct on Contact Manager code paths.
New or modified PHP files in wp-content/uploads/ or plugin directories following anomalous POST requests.
Outbound network connections originating from the WordPress PHP process to unfamiliar hosts.

Detection Strategies

Inspect web server access logs for request bodies and query strings containing PHP serialization patterns targeting contact-manager routes.
Deploy Web Application Firewall (WAF) rules that flag serialized object syntax in requests to WordPress admin-ajax and plugin handlers.
Compare installed plugin versions against the patched release and alert on any host still running 9.1.1 or earlier.

Monitoring Recommendations

Forward WordPress, PHP-FPM, and web server logs to a centralized analytics platform for correlation across sites.
Monitor file integrity in plugin, theme, and uploads directories for unauthorized changes.
Track newly created administrator accounts, scheduled tasks (wp_cron), and option table modifications.

How to Mitigate CVE-2025-68853

Immediate Actions Required

Update the Kleor Contact Manager plugin to a version later than 9.1.1 as soon as a fixed release is available from the vendor.
If no patched version exists, deactivate and remove the plugin from all WordPress installations.
Audit affected sites for indicators of compromise, including unexpected admin users, modified files, and unknown scheduled jobs.

Patch Information

Review the Patchstack Vulnerability Report for the latest patch availability and remediation status. Apply vendor updates through the WordPress dashboard or by replacing plugin files manually after verification.

Workarounds

Block requests containing PHP serialization markers (O:, a:) destined for Contact Manager endpoints at the WAF or reverse proxy layer.
Restrict access to plugin endpoints by IP allow-listing where feasible.
Disable the plugin until a patched version is installed and verified in a staging environment.

bash

# Configuration example: WAF rule to block serialized PHP payloads to Contact Manager
SecRule REQUEST_URI "@contains contact-manager" \
    "chain,phase:2,deny,status:403,id:1006853,\
    msg:'Possible PHP Object Injection - CVE-2025-68853'"
    SecRule ARGS|REQUEST_BODY|REQUEST_COOKIES "@rx O:[0-9]+:\"[A-Za-z_\\\\]+\":[0-9]+:"