Advanced JavaScript Recon for Bug Bounty

From Basic Enumeration to $50K+ Critical Findings
JavaScript reconnaissance is one of the most underestimated attack vectors in modern bug bounty and penetration testing .
Most researchers follow the same boring workflow, run the same tools, and get the same low-impact results.

Elite researchers think differently.
They treat JavaScript as an intelligence goldmine, not just static files.

This framework shows how advanced hunters turn JS analysis into high-impact critical vulnerabilities.

Why Basic JavaScript Recon Fails​

The problem isn’t the tools - it’s the mindset .
Most workflows look like this:

• Enumerate subdomains
• Crawl endpoints
• Download JavaScript
• Grep for secrets

Result?
You find exactly what 10,000 other researchers already found.
To uncover real bugs, you must:

• Build context
• Track relationships
• Understand application logic

---

​

Phase 1: Multi-Dimensional Subdomain Intelligence​

The goal here is not just enumeration - it’s building an attack graph .
You want:

• Old subdomains
• Forgotten environments
• Hidden infrastructure

These often load new JavaScript with old security assumptions.

Aggressive Multi-Source Discovery​

TARGET="example.com"
DATE=$(date +%Y%m%d_%H%M%S)

subfinder -d $TARGET -all -recursive -silent | anew subs.txt
github-subdomains -d $TARGET -t $TOKEN -e -raw | anew subs.txt
assetfinder --subs-only $TARGET | anew subs.txt

Certificate Transparency Time Travel​

curl -s "crt.sh/?q=%.$TARGET&output=json" | \
jq -r '.[].name_value' | sed 's/\*\.//g' | anew subs.txt

Smart DNS Bruteforce Using Real Patterns​

cat subs.txt | sed 's/\..*$//' | sort -u > patterns.txt
puredns bruteforce patterns.txt $TARGET -r resolvers.txt -w bruteforce.txt

Hidden Infrastructure via Shodan & Censys​

shodan domain $TARGET | grep -oP '(?<=Subdomain: )\S+' | anew subs.txt

Key Insight
Old subdomains + new JavaScript often mean outdated dependencies and known CVEs.

---

​

Phase 2: Intelligent Asset Classification​

Don’t just check if a host is alive - fingerprint everything .
You want to know:

• Frameworks
• CDN usage
• Backend technologies
• Hash changes

cat subs.txt | httpx -silent -json -td -cdn -title -tech-detect \
-status-code -content-length -hash sha256 -o httpx_intel.json

Extract High-Value Targets by Tech Stack​

jq -r 'select(.tech[]? | contains("Next.js")) | .url' httpx_intel.json > nextjs.txt
jq -r 'select(.tech[]? | contains("React")) | .url' httpx_intel.json > react.txt
jq -r 'select(.tech[]? | contains("GraphQL")) | .url' httpx_intel.json > graphql.txt

Key Insight
Each tech stack has predictable bug classes:

• Next.js → Authorization bypass & cache poisoning
• React → DOM-based XSS
• GraphQL → Introspection & access control flaws

---

​

Phase 3: Context-Aware URL Discovery​

Crawling without context wastes time .
You need:

• Historical endpoints
• Deleted APIs
• Parameterized routes

Deep Crawling with History​

cat httpx_intel.json | jq -r '.url' > alive.txt

katana -u alive.txt -d 5 -ps -pss waybackarchive,commoncrawl \
-f qurl -jc -kf all -aff \
-ef woff,css,png,svg,jpg,gif -o katana.txt

Wayback Time-Travel​

cat alive.txt | waybackurls | uro | anew wayback.txt

Parameter Mining​

paramspider --domain example.com --level high --output params.txt

API Version Extraction​

cat katana.txt wayback.txt params.txt | \
grep -Eo '/v[0-9]+/|/api/v[0-9]+/' | sort -u > api_versions.txt

Critical Insight
Old API versions often lack:

• Rate limiting
• Authorization checks
• Modern security headers

---

​

Phase 4: Surgical JavaScript Extraction​

JavaScript files are not equal .
You must classify and prioritize.

Build a JavaScript Intelligence Database​

cat katana.txt wayback.txt params.txt | \
grep -iE '\.(js|jsx|mjs|ts|tsx)(\?|$)' | \
httpx -silent -mc 200 -json -hash sha256 \
-content-length -o js_metadata.json

High-Value JS by Size​

jq -r 'select(.content_length > 100000) | .url' js_metadata.json > large_js.txt

Sensitive Paths Detection​

jq -r '.url' js_metadata.json | \
grep -iE '(admin|internal|debug|test|dev|staging)' > sensitive_js.txt

Source Map Extraction​

jq -r '.url' js_metadata.json | sed 's/\.js$/.js.map/' | \
httpx -silent -mc 200 -o sourcemaps.txt

Advanced Insight
Source maps can expose:

• Original source code
• API keys
• Feature flags
• Internal logic

---

​

Final Thoughts for Serious Researchers​

Advanced JavaScript reconnaissance is about:

• Context
• Correlation
• Strategy

Not speed .
If you master this framework, JavaScript stops being noise - and becomes your highest-impact attack surface.