Github subdomain takeover

reward: 200$

Description

A subdomain takeover is when a misconfigured Domain Name System (DNS) record is re-registered to an endpoint owned by an attacker. An attacker is then able to redirect users to the endpoint and capture data such as cookies and credentials, perform Cross-Site Scripting (XSS) attacks, and potentially take over accounts in the legitimate application.

A subdomain takeover vulnerability was identified which could impact the reputation and brand of the business. An attacker can register a subdomain on behalf of the target domain and use it for spamming and phishing attacks.

Business Impact

Subdomain takeover can lead to data theft and indirect financial loss through the attacker’s ability to interact with legitimate users. These malicious actions could also result in reputational damage for the business through the impact to customers’ trust.

Steps to Reproduce

1. Go to new repository page
2. Set Repository name to canonical domain name (i.e., {something}.github.io from CNAME record)
3. Click Create repository
4. Push content using git to a newly created repo. GitHub itself provides the steps to achieve it
5. Switch to Settings tab
6. In GitHub Pages section choose master branch as source
7. Click Save
8. After saving, set Custom domain to source domain name (i.e., the domain name which you want to take over)
9. Click Save

PoC

Status

Resolved