CVE-2026-57713: Events Manager Object Injection Vulnerability

CVE-2026-57713 Overview

CVE-2026-57713 is a PHP Object Injection vulnerability in the Events Manager WordPress plugin maintained by Marcus (aka @msykes). The flaw stems from deserialization of untrusted data [CWE-502] and affects all plugin versions up to and including 7.3.6. Attackers can send crafted serialized payloads over the network to trigger object instantiation inside the WordPress process. Successful exploitation can lead to arbitrary code execution, file manipulation, or full site compromise when a suitable POP (property-oriented programming) chain exists in the WordPress core, other plugins, or themes.

Critical Impact
Network-reachable object injection in Events Manager <= 7.3.6 can result in high-impact compromise of confidentiality, integrity, and availability on affected WordPress sites.

Affected Products

Events Manager WordPress plugin (events-manager) by Marcus (@msykes)
All versions from initial release through 7.3.6
WordPress installations that expose plugin functionality to unauthenticated or low-privilege users

Discovery Timeline

2026-07-13 - CVE-2026-57713 published to NVD
2026-07-13 - Last updated in NVD database

Technical Details for CVE-2026-57713

Vulnerability Analysis

The Events Manager plugin passes user-controlled input to a PHP deserialization routine without validating the object types being reconstructed. When PHP calls unserialize() on attacker-supplied data, it instantiates arbitrary classes present in the runtime and invokes their magic methods such as __wakeup, __destruct, or __toString. Attackers chain these methods across loaded classes to build a property-oriented programming gadget. The result is arbitrary code execution, file read or write, or database tampering inside the WordPress process. The Patchstack advisory tracks this issue as a PHP Object Injection vulnerability in versions up to 7.3.6.

Root Cause

The root cause is unsafe deserialization of untrusted input. The plugin trusts serialized data received through request parameters, cookies, or stored fields and passes it directly to unserialize(). PHP has no built-in allow-list for classes during deserialization by default, so any class autoloadable at that point in execution becomes a candidate gadget.

Attack Vector

Exploitation is remote and requires user interaction according to the CVSS vector. An attacker crafts a serialized PHP object payload targeting a known gadget chain and delivers it to a vulnerable endpoint exposed by Events Manager. When the plugin deserializes the payload, the gadget chain executes attacker-controlled logic in the WordPress worker process. Because the CVSS scope is unchanged and impacts are high across confidentiality, integrity, and availability, a successful attack typically yields full site takeover.

No verified public proof-of-concept code is available. For technical details refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2026-57713

Indicators of Compromise

Requests to Events Manager endpoints containing serialized PHP markers such as O:, a:, or s: in parameter values or cookies
Unexpected PHP files, webshells, or modified plugin and theme files under wp-content/
New administrator accounts, altered wp_options entries, or scheduled cron tasks introduced without change control
PHP errors referencing __wakeup, __destruct, or unserialization warnings in web server logs

Detection Strategies

Inspect HTTP request bodies, query strings, and cookies for base64-encoded or raw PHP serialization signatures targeting Events Manager routes
Correlate WordPress debug.log deserialization warnings with outbound network connections from the PHP worker
Baseline plugin file hashes and alert on deviations across wp-content/plugins/events-manager/

Monitoring Recommendations

Enable a web application firewall rule set that flags PHP object injection patterns on WordPress endpoints
Forward WordPress, PHP-FPM, and web server logs to a centralized analytics platform for correlation with process and file integrity telemetry
Monitor for new PHP processes spawning shells or writing to plugin, theme, or upload directories

How to Mitigate CVE-2026-57713

Immediate Actions Required

Identify all WordPress sites running Events Manager <= 7.3.6 and prioritize patching
Update Events Manager to a fixed release once published by the maintainer per the Patchstack advisory
Restrict network exposure of vulnerable endpoints using WAF rules while patching is in progress
Rotate WordPress secrets, administrator passwords, and API keys if compromise is suspected

Patch Information

Refer to the Patchstack Vulnerability Report for the current fixed version guidance. Apply the vendor-supplied update through the WordPress plugin manager or by replacing plugin files from the official repository.

Workarounds

Temporarily disable and remove the Events Manager plugin on sites that cannot be patched immediately
Deploy WAF signatures that block PHP serialization payloads (O:, a:, s:) on plugin request paths
Restrict access to plugin endpoints by IP allow-list or authentication where feasible until the patched version is deployed

bash

# Example: block requests containing PHP object injection markers via ModSecurity
SecRule ARGS|REQUEST_COOKIES|REQUEST_BODY "@rx (?:^|[^a-zA-Z0-9])O:\d+:\"[A-Za-z_\\\\]+\":\d+:" \
    "id:1057713,phase:2,deny,status:403,log,msg:'Possible PHP Object Injection targeting Events Manager (CVE-2026-57713)'"