hunt-cors
hunt-cors identifies Cross-Origin Resource Sharing misconfigurations that allow attackers to read sensitive authenticated data from a victim's browser. Test this skill against API endpoints, single-page applications, and services that emit Access-Control headers to verify whether reflected origins, null-origin trust, subdomain-regex bypasses, or postMessage handlers enable credentialed cross-origin requests. A finding requires browser proof that response bodies are readable from an attacker-controlled origin combined with valid credentials.
git clone --depth 1 https://github.com/elementalsouls/Claude-BugHunter /tmp/hunt-cors && cp -r /tmp/hunt-cors/skills/hunt-cors ~/.claude/skills/hunt-corsSKILL.md
# HUNT-CORS — Cross-Origin Resource Sharing Misconfiguration
## What actually pays (and what does not)
CORS pays High **only** when an attacker-controlled origin can perform a
**credentialed** cross-origin read of sensitive authenticated data, and you
have a browser PoC proving the response body is readable from `evil.com`.
Two hard browser rules that kill most "findings" — check these FIRST:
- **`Access-Control-Allow-Origin: *` CANNOT be combined with credentials.**
If the server returns `ACAO: *`, the browser refuses to send/expose the
response for a `credentials: include` request. A wildcard-only endpoint is
**not** credential-exploitable. It is only interesting if the data it serves
is sensitive *without* a session (rare) — usually this is Informational/Low.
- **`Access-Control-Allow-Credentials: true` is meaningless on its own.** It
matters only if `ACAO` reflects/allows your specific attacker origin AND a
cross-origin credentialed `fetch` actually returns a readable body. ACAC on a
response that does not reflect your origin proves nothing.
If you cannot demonstrate a readable cross-origin authed body in a real
browser, you do not have a High. Do not submit header-diffing alone.
---
## Crown Jewel Targets
- **Reflect-any-origin + credentials** — server echoes the `Origin` header AND
sets `ACAC: true` → any site reads authed API responses. The classic High.
- **Null-origin trust** — `ACAO: null` + `ACAC: true`. A `sandbox` iframe (or a
`data:`/redirect chain) emits `Origin: null`, so any page can read authed data.
- **Subdomain-regex bypass** — trusted-origin regex with a parsing flaw. The
correct payload depends on *which* flaw (see Phase 3 — this is where most
skills get it wrong).
- **Subdomain takeover → trusted origin** — a dangling subdomain that the CORS
policy trusts; take it over, host the PoC there (see hunt-subdomain).
- **postMessage missing/loose origin check** — handler that processes
`event.data` without strictly validating `event.origin`.
---
## Attack Surface Signals
```
Any endpoint returning an Access-Control-Allow-Origin header
API endpoints: /api/*, /v1/*, /graphql
Profile/account: /api/me, /api/profile, /api/user, /api/session
Secrets/tokens: /api/tokens, /api/keys, /api/csrf, /api/account/settings
Financial: /api/balance, /api/transactions
Admin/internal: /api/admin/*, /api/internal/*
```
Prioritize endpoints that (a) require a session cookie and (b) return PII,
tokens, CSRF tokens, or other secrets in the body.
---
## Step-by-Step Hunting Methodology
### Phase 1 — Discover CORS endpoints
```bash
# Probe API endpoints. Use GET (not -I): some servers only emit CORS on GET,
# and -I sends HEAD which may be handled differently.
while read url; do
result=$(curl -s -D - -o /dev/null "$url" \
-H "Origin: https://evil.com" \
-H "Cookie: $SESSION_COOKIE" | grep -i "access-control")
[ -n "$result" ] && echo "=== $url ===" && echo "$result"
done < recon/$TARGET/api-endpoints.txt
# httpx bulk check
cat recon/$TARGET/live-hosts.txt | awk '{print $1}' | \
httpx -H "Origin: https://evil.com" -match-string "access-control-allow-origin"
```
### Phase 2 — Reflect-any-origin + null origin
```bash
# Does the server reflect an arbitrary Origin back?
curl -s -D - -o /dev/null https://$TARGET/api/me \
-H "Origin: https://evil.com" \
-H "Cookie: $SESSION_COOKIE" | grep -i "access-control"
# Vulnerable (the High case):
# Access-Control-Allow-Origin: https://evil.com <- reflects attacker origin
# Access-Control-Allow-Credentials: true <- + credentials => readable
#
# NOT exploitable for credentialed theft:
# Access-Control-Allow-Origin: * <- browser blocks creds read
# (no ACAC, or ACAC absent) <- not credentialed
# Null-origin trust
curl -s -D - -o /dev/null https://$TARGET/api/me \
-H "Origin: null" \
-H "Cookie: $SESSION_COOKIE" | grep -i "access-control"
# Looking for: Access-Control-Allow-Origin: null + ACAC: true
```
### Phase 3 — Subdomain / trusted-origin regex bypass
The right payload depends on **which** regex flaw the server has. Identify the
class first, then send the matching payload. Getting this wrong wastes the test
and produces false negatives.
| Server regex (intended: trust `*.target.com`) | Flaw | Bypass origin that matches | Why |
|---|---|---|---|
| `^https?://.*\.target\.com$` | **None** — escaped dot + end-anchor. Correct. | (no simple bypass) | `evil.target.com` is in-scope by design; `x.target.com.evil.com` ENDS in `.evil.com`, fails `$`. Move on or look for subdomain-takeover. |
| `^https?://.*target\.com$` | **Missing dot separator** (no `\.` before `target`) | `https://eviltarget.com` | `.*target\.com$` matches `eviltarget.com` — attacker registers `eviltarget.com`. |
| `^https?://.*\.target\.com` | **Missing end-anchor `$`** | `https://x.target.com.evil.com` | regex matches a prefix; `.target.com` appears, then `.evil.com` is ignored (no `$`). |
| `^https?://target\.com` | **Prefix-only, no `$`** | `https://target.com.evil.com` | matches the `target.com` prefix; the rest is unconstrained. |
| `^https?://.*\.target\.com$` but dot in regex is **unescaped** (`.*.target.com$`) | **Unescaped dot** = "any char" | `https://xtargetXcom...` style, or `https://evilZtargetZcom` where `Z` is any single char | `.` matches any character, widening the match. |
| Any of the above | **Special chars browsers send in Origin** | `https://target.com%60.evil.com`, `https://target.com\x60evil.com` | some parsers treat backtick/underscore as letters; Safari/older browsers may emit unusual origins. Confirm the browser actually sends it. |
```bash
# Send each class-specific payload and watch what the server reflects.
for ORIGIN in \
"https://evil.target.com" \
"https://eviltarget.com" \
"https://x.target.com.evil.com" \
"https://target.com.evil.com" \
"https://target.com%60.evil.com" \
"http://target.com"; do
RESULT=$(curl -sEnd-to-end Android APK red-team pipeline — automated APK acquisition (Play Store + apkpure + apkmirror fallback), jadx decompilation, secret/URL/JWT/Firebase grep, pinned-cert extraction, exported-component enumeration, Frida runtime instrumentation templates, intent-injection probes. Built from an authorized external red-team engagement where 7 APKs were pulled manually, 4 download attempts truncated, and a hardcoded JWT + 30 internal API endpoints were recovered from one of the apps. Use when target has a mobile app catalogue (Play Store developer page), when you find an APK URL hosted on a web server, or when post-recon mentions "mobile app" in scope.
Run autonomous hunt loop on a target — scope check → recon → rank surface → hunt → validate → report with configurable checkpoints. Usage: /autopilot target.com [--paranoid|--normal|--yolo]
Local-tooling companion to the bug-bounty orchestrator — carries the SAME complete bug-bounty workflow, but reach for THIS variant when you also need to resolve where tools, wordlists, and clones are installed on the local machine (jhaddix, SecLists, trufflehog, ffuf, dalfox, ghauri); for pure orchestration/routing use the bug-bounty skill. Workflow it covers — recon (subdomain enumeration, asset discovery, fingerprinting, HackerOne scope, source code audit), pre-hunt learning (disclosed reports, tech stack research, mind maps, threat modeling), vulnerability hunting (IDOR, SSRF, XSS, auth bypass, CSRF, race conditions, SQLi, XXE, file upload, business logic, GraphQL, HTTP smuggling, cache poisoning, OAuth, timing side-channels, OIDC, SSTI, subdomain takeover, cloud misconfig, ATO chains, agentic AI), LLM/AI security testing (chatbot IDOR, prompt injection, indirect injection, ASCII smuggling, exfil channels, RCE via code tools, system prompt extraction, ASI01-ASI10), A-to-B bug chaining (IDOR→auth bypass, SSRF→cloud metadata, XSS→ATO, open redirect→OAuth theft, S3→bundle→secret→OAuth), bypass tables (SSRF IP bypass, open redirect bypass, file upload bypass), language-specific grep (JS prototype pollution, Python pickle, PHP type juggling, Go template.HTML, Ruby YAML.load, Rust unwrap), and reporting (7-Question Gate, 4 validation gates, human-tone writing, templates by vuln class, CVSS 3.1, PoC generation, always-rejected list, conditional chain table, submission checklist). Use when you need the local install path of a tool / wordlist / clone for a hunt, or as the full-workflow variant when operating from this local toolkit; for general routing use the bug-bounty skill. 中文触发词：漏洞赏金、安全测试、渗透测试、漏洞挖掘、信息收集、子域名枚举、XSS测试、SQL注入、SSRF、安全审计、漏洞报告
Use at the START of any bug bounty hunting session, when switching targets, or when feeling lost about what to do next. Master orchestrator that combines the 5-phase non-linear hunting workflow with the critical thinking framework (developer psychology, anomaly detection, What-If experiments). Routes to all other skills based on current hunting phase. Also use when asking "what should I do next" or "where am I in the process.
Complete bug bounty workflow — recon (subdomain enumeration, asset discovery, fingerprinting, HackerOne scope, source code audit), pre-hunt learning (disclosed reports, tech stack research, mind maps, threat modeling), vulnerability hunting (IDOR, SSRF, XSS, auth bypass, CSRF, race conditions, SQLi, XXE, file upload, business logic, GraphQL, HTTP smuggling, cache poisoning, OAuth, timing side-channels, OIDC, SSTI, subdomain takeover, cloud misconfig, ATO chains, agentic AI), LLM/AI security testing (chatbot IDOR, prompt injection, indirect injection, ASCII smuggling, exfil channels, RCE via code tools, system prompt extraction, ASI01-ASI10), A-to-B bug chaining (IDOR→auth bypass, SSRF→cloud metadata, XSS→ATO, open redirect→OAuth theft, S3→bundle→secret→OAuth), bypass tables (SSRF IP bypass, open redirect bypass, file upload bypass), language-specific grep (JS prototype pollution, Python pickle, PHP type juggling, Go template.HTML, Ruby YAML.load, Rust unwrap), and reporting (7-Question Gate, 4 validation gates, human-tone writing, templates by vuln class, CVSS 3.1, PoC generation, always-rejected list, conditional chain table, submission checklist). Use for ANY bug bounty task — starting a new target, doing recon, hunting specific vulns, auditing source code, testing AI features, validating findings, or writing reports. 中文触发词：漏洞赏金、安全测试、渗透测试、漏洞挖掘、信息收集、子域名枚举、XSS测试、SQL注入、SSRF、安全审计、漏洞报告
Bugcrowd-specific reporting tactics complementing report-writing: VRT category search-and-fallback strategy when no exact match exists, manual severity override when VRT defaults underrate impact, severity-request paragraph as first body section, OOS-clause rebuttal templates (rate limiting on auth-flow endpoints, debug-info framing, user-enumeration with sensitive PII, theoretical-issue counter), chained-finding cross-reference patterns, target selection for QA-vs-prod programs, researcher-side hygiene (Bugcrowdninja email alias, account state restoration, friendly-tester posture). Use when filing a Bugcrowd submission, when VRT default seems wrong, when triager closes as OOS or downgrades severity, when chaining linked submissions, or when scope distinguishes production from QA. Pairs with report-writing and triage-validation.
Build an exploit chain — given bug A, finds B and C to combine for higher severity and payout. Knows common chain patterns: IDOR→ATO, SSRF→cloud metadata, XSS→ATO, open redirect→OAuth theft, S3→bundle→secret→OAuth. Usage: /chain
Cloud IAM red-team attack chain across AWS, Azure, GCP — focused on EXTERNAL exploitation paths and post-credential-discovery privilege analysis. Covers IAM enumeration (aws iam, az role, gcloud iam), STS/AssumeRole chaining, Azure Managed Identity abuse (via SSRF/leak), GCP service account JSON abuse, IMDSv1/v2 attacks via SSRF, K8s ServiceAccount token privilege analysis once held (token discovery / cluster exposure is owned by hunt-k8s), role-trust-policy confused-deputy, cross-account assume-role enumeration, IAM privilege escalation patterns (24+ AWS, 8+ Azure, 6+ GCP), and AWS Cognito Identity Pool unauthenticated-role attack chain (GetId → GetCredentialsForIdentity → IAM role abuse). Built for the case where recon yields a credential (key, JSON, token) and you need to know what it grants and how to escalate. Use when an AWS key / Azure secret / GCP service account JSON / K8s SA token surfaces from a code repo, JS bundle, APK, breach corpus, or SSRF chain.