In the vast world of web vulnerabilities, Broken Link Hijacking (BLH) is a subtle yet potent risk that many organizations overlook — often until it’s too late. I recently discovered such a vulnerability on my own organization’s corporate website, and it served as a sharp reminder of how something as innocuous as a dead link can open the door to malicious exploitation.

What is Broken Link Hijacking?

Broken Link Hijacking occurs when a website references an external resource — such as a script, stylesheet, or image — hosted on a third-party domain that is no longer registered or accessible. If that domain becomes available, an attacker can register it and host malicious content at the same path, effectively “hijacking” the link.

This could allow the attacker to:

• Serve malicious JavaScript for XSS or malware delivery
• Harvest visitor analytics or credentials
• Damage brand reputation or SEO
• Conduct phishing through impersonation of the hijacked resource

Real-World Discovery: A Case from the Field

While performing routine audits of our corporate web assets, I used tools like 404 scanners and external link analyzers (think: BrokenLinkCheck, Ahrefs, Burp Suite’s link mapper, and custom Python scripts) to identify dangling references on high-traffic pages.

One of the broken links pointed to a stylesheet hosted on a third-party subdomain — a domain that had expired and was available for re-registration.

That’s all it would take — one malicious actor to claim the domain, upload a crafted stylesheet or script, and potentially compromise every visitor accessing that page.

Fixing the Issue: Responsible Remediation

Once the issue was identified:

1. The link was removed from the affected pages.
2. We scanned other assets for similar outdated references.
3. A domain monitoring alert was set up to watch for abandoned third-party resources.
4. Our DevOps team was briefed to implement a process for reviewing external links during deployment cycles.

This was a small win, but it highlights the importance of proactive vigilance in security hygiene.

Tools and Techniques to Detect Broken Link Hijacking

Here are some tools and methods you can use to detect and prevent BLH:

• Automated Link Crawlers: Tools like Screaming Frog SEO Spider, Xenu, or Ahrefs can identify 404s and external domains.
• Burp Suite: Use passive scanning to log external dependencies and identify dead links.
• Custom Scripting: Write a Python crawler to parse site HTML and test response codes.
• WHOIS Lookups + DNS Monitoring: Check if linked domains are unregistered or expiring soon.
• CI/CD Pipeline Integration: Incorporate external link validation as part of your deployment process.

Proactive Defense Tips

• Avoid hardcoding third-party resources where possible. Prefer self-hosting critical assets.
• Regularly audit all external links and third-party scripts.
• Use Content Security Policy (CSP) headers to limit what external domains can execute on your site.
• Monitor domain expiry and set up alerts for key vendors and linked services.
• Educate dev teams on the risks of dangling links and orphaned assets.

Final Thoughts

Broken Link Hijacking may not make headlines like zero-days or ransomware, but its silent potential for abuse makes it a serious security concern — especially for high-trust, high-traffic websites. It’s the kind of vulnerability that thrives on negligence.

I encourage all IT managers, developers, and security professionals to include external link hygiene in their regular security audits. You might just find a ticking time bomb hiding in plain sight — as I did.

Stay sharp, stay secure.