High Impact Subdomain Takeover

High-Impact Subdomain Takeover

Overview of the Vulnerability

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 high-impact 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 to create a HTML document with JavaScript payload that triggers a Cross-Site Scripting (XSS) attack. The target domain can also be used to create a scenario where an attacker can harvest user credentials by phishing users who then visit and login on a cloned version of a legitimate website.

Business Impact

High-Impact subdomain takeover could 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. Browse to the URL takeover.inscope.com/proof.txt

2. You will see a Bugcrowd Username which matches the HTML comment in the Proof of Concept

Proof of Concept (PoC)

The following screenshot show the success of a subdomain takeover:

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Guidance

Provide a step-by-step walkthrough with a screenshot on how you exploited the vulnerability. This will speed triage time and result in faster rewards.

Subdomain takeovers require some form of evidence that can be viewed by the team who triage this vulnerability, once you have taken over the subdomain, hosting a file containing your Bugcrowd username or the submission ID will be sufficient. Place this username or submission ID inside of a HTML comment.

Describe the impact of the takeover from this subdomain to the company, what effect would this have towards their operations, their public image, how frequently is this domain used, is this meant to be public facing?