Subdomain takeovers are an important vulnerability to be familiar with, especially as a bug bounty hunter.
Introduction
Subdomain takeovers occur when a subdomain (e.g. blog.example.com) is pointing to a service (e.g. blog.example.com is hosted on a blogging platform like WordPress) that the attacker no longer has control over.
This can happen when the original owner of the subdomain stops using the service or cancels their account, but forget to update the DNS records to reflect this.
Security Risks
An attacker can then register the abandoned service account and gain control over the subdomain. This can allow them to host malicious content, phish for user information, or redirect traffic to their own sites.
MX takeover is a specific type of subdomain takeover that occurs when an attacker gains control over an organization’s email subdomain. This can allow the attacker to intercept, read, and potentially modify emails sent to and from the organization.
Remediation
To prevent subdomain takeovers, it is important for organizations to regularly check their DNS records and ensure that all subdomains are still in use and properly configured.
One tool that can help with this is MX Takeover, which is a Go script available on GitHub (https://github.com/musana/mx-takeover). This tool can scan a list of subdomains and check for potential MX takeover vulnerabilities.
Preventing subdomain takeovers is an important aspect of overall cybersecurity hygiene, as it can help protect an organization’s sensitive data and prevent the spread of malicious content.
By using tools such as MX Takeover, organizations can proactively identify and address potential vulnerabilities in their subdomains.
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