CVE-2026-73341: RegistrationMagic Auth Bypass Vulnerability

CVE-2026-73341 Overview

CVE-2026-73341 is an unauthenticated PHP Object Injection vulnerability in the RegistrationMagic WordPress plugin (Custom Registration Form Builder with Submission Manager). Versions 6.0.9.7 and earlier deserialize attacker-controlled input without validation, mapping to [CWE-502] Deserialization of Untrusted Data. Remote attackers can inject crafted serialized PHP objects over the network without authentication or user interaction. When a suitable POP (Property-Oriented Programming) gadget chain is present in the WordPress core or other installed plugins, exploitation can lead to remote code execution, arbitrary file operations, or full site compromise.

Critical Impact
Unauthenticated attackers can trigger PHP object deserialization on vulnerable WordPress sites and, with a viable gadget chain, achieve remote code execution and full site takeover.

Affected Products

RegistrationMagic (Custom Registration Form Builder with Submission Manager) WordPress plugin, versions <= 6.0.9.7
WordPress sites running the affected plugin versions
Any hosting environment executing the vulnerable plugin under PHP

Discovery Timeline

2026-08-18 - CVE-2026-73341 published to NVD
2026-08-20 - Last updated in NVD database

Technical Details for CVE-2026-73341

Vulnerability Analysis

The flaw stems from unsafe handling of serialized data inside RegistrationMagic. The plugin passes untrusted input to PHP's unserialize() function without validating structure, type, or origin. When PHP deserializes a serialized object, it reconstructs it and invokes magic methods such as __wakeup(), __destruct(), and __toString(). Attackers abuse this behavior by supplying a serialized object whose class exists in the runtime and whose magic methods perform sensitive operations. Because the plugin exposes the sink to unauthenticated requests, no account or user interaction is required to trigger deserialization on the target host.

Root Cause

The root cause is direct deserialization of attacker-controlled data with unserialize() and no allowlist of expected classes. The plugin does not use json_decode() or pass ['allowed_classes' => false] to unserialize(). Combined with WordPress and third-party plugins loading many classes, this creates the conditions for a POP gadget chain. The vulnerability is classified under [CWE-502] Insecure Deserialization.

Attack Vector

Exploitation is network-based. An attacker sends an HTTP request to an exposed RegistrationMagic endpoint with a crafted serialized payload in a parameter reaching the vulnerable sink. PHP reconstructs the object graph, invoking magic methods on classes present in the site. Depending on available gadgets, this can escalate to arbitrary file writes, arbitrary file deletion, SQL execution, or command execution. See the Patchstack Vulnerability Report for advisory details.

No verified public proof-of-concept code is available at this time. The vulnerability mechanism is described above; technical specifics remain with the reporting vendor.

Detection Methods for CVE-2026-73341

Indicators of Compromise

HTTP requests to RegistrationMagic endpoints containing serialized PHP payload markers such as O:, a:, s:, or C: followed by class and length descriptors.
Unexpected PHP worker crashes, fatal errors referencing __wakeup, __destruct, or unserialize() in web server logs.
New or modified PHP files under wp-content/uploads/, wp-content/plugins/, or the site webroot without a corresponding administrative action.
Creation of unexpected WordPress administrator accounts or scheduled tasks following anomalous plugin traffic.

Detection Strategies

Inspect web application firewall and reverse proxy logs for request bodies or query parameters containing serialized PHP object patterns targeting RegistrationMagic routes.
Alert on outbound network connections initiated by PHP-FPM or Apache worker processes to previously unseen destinations after requests to the plugin.
Correlate WordPress audit logs for privilege changes, option updates, and plugin activations that follow anonymous requests to registration endpoints.

Monitoring Recommendations

Enable verbose PHP error logging and forward logs to a centralized platform for anomaly analysis.
Monitor filesystem integrity for the WordPress installation directory using file integrity monitoring tooling.
Track process lineage on WordPress hosts to identify shells or interpreters spawned by web server users.

How to Mitigate CVE-2026-73341

Immediate Actions Required

Update RegistrationMagic to a version newer than 6.0.9.7 as soon as the vendor releases a fixed build.
If a patched version is not yet available, deactivate and remove the RegistrationMagic plugin from production WordPress sites.
Restrict access to registration and form submission endpoints at the WAF or reverse proxy layer until patching is complete.
Audit WordPress administrator accounts, scheduled tasks (wp_cron), and recently modified files for signs of prior exploitation.

Patch Information

Refer to the Patchstack Vulnerability Report for authoritative remediation guidance and the fixed version once published by the plugin vendor. Apply the update through the WordPress admin dashboard or via wp-cli.

Workarounds

Deploy WAF rules that block request parameters containing PHP serialized-object patterns such as O:\d+:" and a:\d+:{.
Enforce authentication or IP allowlisting on the registration endpoints exposed by the plugin.
Disable the plugin site-wide via wp-cli plugin deactivate custom-registration-form-builder-with-submission-manager until an official fix is applied.

bash

# Deactivate the vulnerable plugin using wp-cli
wp plugin deactivate custom-registration-form-builder-with-submission-manager

# Optional: remove the plugin entirely
wp plugin uninstall custom-registration-form-builder-with-submission-manager

# Verify plugin status
wp plugin list --status=active