Summary

An unsafe deserialization vulnerability allows any unauthenticated user to execute arbitrary code on the server.

PoC

1. Go to
   https://www.admidio.org/demo_en/adm_program/modules/messages/messages.php
2. Click on Send Private Message
3. In the Message field, enter the following payload
   Testing<br><h1>HTML</h1><br><h2>Injection</h2>

4. Send the message
5. Open the message again

Impact

1. Data Theft: Stealing sensitive information like cookies, session tokens, and user credentials.
2. Session Hijacking: Gaining unauthorized access to user accounts.
3. Phishing: Tricking users into revealing sensitive information.
4. Website Defacement: Altering the appearance or content of the website.
5. Malware Distribution: Spreading malware to users' devices.
6. Denial of Service (DoS): Overloading the server with malicious requests.