User Frontend: AI Powered Frontend Posting, User Directory, Profile, Membership & User Registration <= 4.3.1 - Authenticated (Subscriber+) PHP Object Injection
Strategic Overview
- Status
- Patched in 4.3.2
- Affected Plugin
- User Frontend – Membership, User Registration, User Profile, User Directory & Content Restriction with Frontend Post Submission
- Affected Version
<= 4.3.1- CVSS
- 8.8High
- Weakness type
- CWE-502 · Deserialization of Untrusted Data
- CVE
CVE-2026-5127
At a glance
CVE-2026-5127 is a high-severity Deserialization of Untrusted Data vulnerability in the User Frontend WordPress plugin, affecting versions <= 4.3.1. It carries a CVSS score of 8.8 (reachable over the network; low attack complexity; high confidentiality, integrity, availability impact). Exploitation requires an authenticated account at Subscriber level or above. The issue is fixed in version 4.3.2; sites on affected versions should update now. Disclosed May 2026, reported by d.v4n_s3c.
Vulnerability Overview
The User Frontend: AI Powered Frontend Posting, User Directory, Profile, Membership & User Registration plugin for WordPress is vulnerable to Deserialization of Untrusted Data in versions up to, and including, 4.3.1 This is due to insufficient input validation and type checking on the wpuf_files parameter during form submission, combined with unconditional deserialization via maybe_unserialize() when displaying post content. This makes it possible for authenticated attackers, with Subscriber-level access and above, to inject arbitrary PHP objects, which can be leveraged to execute arbitrary code, delete arbitrary files, or perform other malicious actions if a POP chain is present on the target system.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, 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
User Frontend <= 4.3.1 carries this weakness at maybe_unserialize(), and reaching it takes an account at Subscriber level or above. 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 Frontend the fix is 4.3.2: builds <= 4.3.1 are affected, anything from 4.3.2 onward is not.
Remediation
Update to version 4.3.2, or a newer patched version
How does WordSec protect against this?
An attacker needs Subscriber access first, so the firewall sees the attempt as traffic from a logged-in account: 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 Frontend 4.3.2 closes this, and updating the plugin is the step that ends it.
- Firewall
- Scanner
- Alerts
External References
Related records
Other vulnerabilities in User Frontend – Membership, User Registration, User Profile, User Directory & Content Restriction with Frontend Post Submission
- 9.8WP User Frontend < 2.3.11 Arbitrary File Upload
- 9.1CVE-2024-38693: WP User Frontend <= 4.0.7 SQL Injection
CVE-2024-38693 - 8.8CVE-2026-1565: User Frontend Arbitrary File Upload
CVE-2026-1565 - 8.8CVE-2023-47682: WP User Frontend <= 3.6.5 Privilege Escalation
CVE-2023-47682 - 8.8CVE-2021-25076: WP User Frontend SQL Injection & Reflected XSS
CVE-2021-25076 - 8.1CVE-2021-24649: WP User Frontend <= 3.5.28 Privilege Escalation
CVE-2021-24649 - 7.2WP User Frontend SQL Injection
- 5.4CVE-2025-58673: WP User Frontend Arbitrary Shortcode Execution
CVE-2025-58673
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