This post is the write-up about subdomain takeover vulnerable service Announcekit that I found. Although this is a paid service, It's possible to create PoC without having to purchase the service during trial period.

Announcekit.app

​AnnounceKit is a user communication platform that helps you announce product updates to increase feature adoption.

Service Detection

CNAME record should be pointing to cname.announcekit.app

akit-tk.melbadry9.xyz.  42      IN      CNAME   cname.announcekit.app.

I use the following Nuclei template to check for possible candidates.

id: detect-announcekit
​
info:
  name: Announcekit service detection
  author: melbadry9
  severity: info
  tags: dns
​
dns:
  - name: "{{FQDN}}"
    type: CNAME
    class: inet
    recursion: true
    retries: 2
    matchers:
      - type: word
        words:
          - "cname.announcekit.app"

Takeover Detection

To verify whether subdomain takeover may be possible we should see a similar error page.

Fingerprint

To detect vulnerable subdomain we use the following fingerprint based on HTTP response we confirm whether subdomain is vulnerable or not.

{
    "status_code": 404,
    "text": [
        "Error 404 - AnnounceKit"
    ]
}

I use the following Nuclei template to check for vulnerable subdomain.

id: announcekit-takeover
​
info:
  name: Announcekit Takeover Detection
  author: melbadry9
  severity: high
  tags: takeover
  reference: https://announcekit.app/docs/custom-host
​
requests:
  - method: GET
    raw:
      - |
        GET / HTTP/2
        Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
    
    redirects: true
    max-redirects: 1
​
    matchers-condition: and
    matchers:
      - type: word
        words:
          - 'Error 404 - AnnounceKit'
      
      - type: status
        status:
          - 404

Takeover Steps

• Register an account on AnnounceKit​

• Go to https://announcekit.app/dashboard/settings/feeds

• Set Custom Hostname to subdomain we want to takeover akit-tk.melbadry9.xyz

• Visit https://kit-tk.melbadry9.xyz

Can I takeover XYZ? - Issue

I have opened an issue on GitHub regarding this service:

​