Strategic Overview
- Status
- Patched in 2.3.3
- Affected Version
<= 2.3.2.1- CVSS
- 7.5High
- Weakness type
- CWE-502 · Deserialization of Untrusted Data
- CVE
CVE-2023-27459
At a glance
CVE-2023-27459 is a high-severity Deserialization of Untrusted Data vulnerability in the User Registration & Membership WordPress plugin, affecting versions <= 2.3.2.1. It carries a CVSS score of 7.5 (reachable over the network; high confidentiality, integrity, availability impact). The issue is fixed in version 2.3.3; sites on affected versions should update now. Disclosed March 2023, reported by Rafie Muhammad.
Vulnerability Overview
The User Registration plugin for WordPress is vulnerable to PHP Object Injection in versions up to, and including, 2.3.2.1 via deserialization of untrusted input in the following functions: ur_get_user_extra_fields, user_registration_form_field. This allows subscriber-level attackers to inject a PHP Object. No POP chain is present in the vulnerable plugin. If a POP chain is present via an additional plugin or theme installed on the target system, it could allow the attacker to delete arbitrary files, retrieve sensitive data, or execute code.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, and no interaction from a victim user. A successful exploit has high impact on confidentiality, integrity, availability — full site compromise territory.
CWE-502: Deserialization of Untrusted Data
Reaching this weakness in User Registration & Membership <= 2.3.2.1 takes a caller who can reach the endpoint. Deserialization of untrusted data means the application reconstructs objects from input a caller controls, letting the attacker choose which classes get instantiated and what their properties hold.
A workable chain turns deserialization into file writes, deletions or code execution, depending on what the loaded classes do in their magic methods. For User Registration & Membership the fix is 2.3.3: builds <= 2.3.2.1 are affected, anything from 2.3.3 onward is not.
Remediation
Update to version 2.3.3, or a newer patched version
How does WordSec protect against this?
The attempt arrives as an ordinary request to User Registration & Membership: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. None of that substitutes for the fix: User Registration & Membership 2.3.3 closes this, and updating the plugin is the step that ends it.
- Firewall
- Scanner
- Alerts
External References
Related records
Other vulnerabilities in User Registration & Membership – Free & Paid Memberships, Subscriptions, Content Restriction, User Profile, Custom User Registration & Login Builder
- 9.9CVE-2023-3342: User Registration <= 3.0.2 Arbitrary File Upload
CVE-2023-3342 - 9.8CVE-2026-32488: User Registration & Membership RCE
CVE-2026-32488 - 9.8CVE-2026-1492: User Registration & Membership Privilege Escalation
CVE-2026-1492 - 9.8CVE-2025-2563: User Registration & Membership Privilege Escalation
CVE-2025-2563 - 8.8CVE-2024-2417: User Registration Authenticated (Subscriber+)
CVE-2024-2417 - 8.8CVE-2022-3912: User Registration <= 2.2.4 Arbitrary File Upload
CVE-2022-3912 - 8.1CVE-2026-11961: User Registration & Membership Privilege Escalation
CVE-2026-11961 - 8.1CVE-2026-1779: User Registration & Membership Authentication Bypass
CVE-2026-1779
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