CVE-2025-48101: Constant Contact WordPress Plugin Flaw

CVE-2025-48101 Overview

CVE-2025-48101 is a PHP Object Injection vulnerability in the Constant Contact for WordPress plugin developed by WebDevStudios. The flaw stems from deserialization of untrusted data [CWE-502] and affects all plugin versions up to and including 4.1.1. Successful exploitation allows attackers to inject arbitrary PHP objects, potentially leading to remote code execution, file deletion, or sensitive data disclosure when a suitable property-oriented programming (POP) chain exists in the WordPress installation.

Critical Impact
An unauthenticated attacker can deliver a crafted serialized payload that, combined with user interaction, triggers object instantiation in the WordPress runtime and compromises site confidentiality, integrity, and availability.

Affected Products

Constant Contact for WordPress plugin (webdevstudios) versions through 4.1.1
WordPress sites running the constant-contact-api plugin
Any WordPress installation where additional plugins or themes provide exploitable POP gadget chains

Discovery Timeline

2025-09-09 - CVE-2025-48101 published to NVD
2026-04-28 - Last updated in NVD database

Technical Details for CVE-2025-48101

Vulnerability Analysis

The vulnerability resides in how the Constant Contact for WordPress plugin processes serialized input. The plugin passes attacker-controlled data to PHP's unserialize() function without sufficient validation. When PHP deserializes the payload, it instantiates objects and invokes magic methods such as __wakeup() and __destruct() on classes loaded in the application context.

If a class with a dangerous magic method exists in WordPress core, another active plugin, or a theme, an attacker can chain those gadgets into a POP chain. The result ranges from arbitrary file writes and deletions to full remote code execution under the web server account.

Root Cause

The root cause is unsafe deserialization of untrusted input [CWE-502]. The plugin trusts serialized data from a request channel and feeds it directly to unserialize(). PHP does not validate object types during deserialization, so any class autoloadable by the application becomes a potential gadget.

Attack Vector

Exploitation occurs over the network and requires user interaction, consistent with the CVSS vector. An attacker crafts a serialized PHP object payload encoding a POP chain. The payload is delivered through a plugin request handler, and a privileged user must trigger the vulnerable flow (for example, by visiting a crafted link or submitting a form). No authentication is required.

Refer to the Patchstack WordPress Vulnerability Report for additional technical context.

Detection Methods for CVE-2025-48101

Indicators of Compromise

HTTP requests to plugin endpoints containing serialized PHP markers such as O:, a:, or s: prefixes in parameter values
Unexpected PHP error log entries referencing unserialize(), __wakeup, or __destruct from the constant-contact-api plugin path
New or modified PHP files in wp-content/uploads/ or plugin directories following suspicious requests
Outbound network connections from the web server to unfamiliar hosts after plugin interaction

Detection Strategies

Inspect web access logs for request bodies and query strings containing serialized object signatures targeting Constant Contact plugin routes
Deploy WAF rules that flag serialized PHP payloads in parameters destined for wp-admin/admin-ajax.php and plugin URIs
Audit installed plugin versions across the WordPress estate to identify hosts running constant-contact-api ≤ 4.1.1

Monitoring Recommendations

Enable PHP error and exception logging and forward logs to a centralized SIEM for correlation
Monitor file integrity in wp-content/plugins/ and wp-content/uploads/ for unauthorized changes
Track administrator session activity and unexpected privilege changes following plugin interaction

How to Mitigate CVE-2025-48101

Immediate Actions Required

Update the Constant Contact for WordPress plugin to a version newer than 4.1.1 once a patched release is available
If no patched version is published, deactivate and remove the plugin from production WordPress sites
Review WordPress administrator accounts and rotate credentials if exploitation is suspected

Patch Information

A fix should be obtained from the plugin vendor through the WordPress plugin repository. Consult the Patchstack advisory for the latest remediation status and patched version details.

Workarounds

Apply virtual patching via a Web Application Firewall to block requests containing serialized PHP object patterns to plugin endpoints
Restrict access to WordPress admin and AJAX endpoints by IP allowlist where feasible
Disable the plugin until a verified patched version is deployed and tested in staging

bash

# Example ModSecurity rule to block serialized PHP payloads to the plugin
SecRule REQUEST_URI "@contains constant-contact" \
    "id:1004810,phase:2,deny,status:403,\
    chain,msg:'Possible PHP Object Injection - CVE-2025-48101'"
    SecRule ARGS "@rx O:[0-9]+:\"[A-Za-z_\\\\]+\":[0-9]+:\\{" \
        "t:none,t:urlDecode"