hpp

hpp is a skill for Claude Code from PurpleAILAB/Decepticon. It costs 25 tokens per session (2,443 once invoked), scanned A, original, Apache-2.0.

A security testing guide for HTTP Parameter Pollution, where duplicate request parameters are interpreted differently by a proxy, security filter, framework, or application. That disagreement can let an unexpected value bypass checks.

In plain words
What is it for?
Testing duplicate query and form parameters for web-application firewall bypasses, parser inconsistencies, and authentication or authorization mistakes.
Why use it?
It helps find cases where one layer validates one parameter value while another layer uses a different value. This can weaken filters or access-control decisions.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Good fit Testing duplicate query and form parameters for web-application firewall bypasses, parser inconsistencies…

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/purpleailab/decepticon/hpp
About the project

Decepticon is an autonomous red-team agent that coordinates AI agents, security tools, sandboxes, and supporting services for authorized cybersecurity assessments. Security researchers and red teams can run it through its Docker stack, cloud service, command-line interface, or Python SDK, with the catalogue entries representing its available skills.

PurpleAILAB/Decepticon · 5,451 stars · on GitHub · decepticon.red

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add PurpleAILAB/Decepticon --skill hpp
Clone the repo
git clone --depth 1 https://github.com/PurpleAILAB/Decepticon

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for hpp

README.md
[![agentmods](https://agentmods.dev/badge/skills/purpleailab/decepticon/hpp.svg)](https://agentmods.dev/skills/purpleailab/decepticon/hpp)
Your own site
<a href="https://agentmods.dev/skills/purpleailab/decepticon/hpp"><img src="https://agentmods.dev/badge/skills/purpleailab/decepticon/hpp.svg" alt="Measured on agentmods" height="20"></a>
Per session 25 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,443 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00025 $0.02443
Opus 5 $0.00013 $0.01222
Sonnet 5 $0.00005 $0.00489
Haiku 4.5 $0.00003 $0.00244

Measured 3d ago against content hash 8d686a182aa1, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

hpp scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

| Python `urllib.parse.parse_qs` | **list** (`["1","2"]`) | — |
packages/decepticon/decepticon/skills/standard/exploit/web/hpp/SKILL.md · 190 lines

How it starts

The opening of the file, as written. The whole thing — 190 lines — stays where its author put it; the contents beside it link to each section on GitHub.

HTTP Parameter Pollution (HPP)

Two layers (proxy/WAF, framework, app code) parse the same duplicate parameter differently. The WAF inspects one value, the app reads another — payload slips through. Or the framework picks one value for the auth check and a different one for the action — ACL bypass. Standalone severity is usually Low/Medium; chained into SQLi / SSRF / auth bypass it is High/Critical.

1. Parser precedence table

When ?id=1&id=2 (or duplicated body params) is received:

Stack request.GET['id'] / equivalent getParameterValues / list view
PHP ($_GET) last wins (2) $_GET['id[]'] only; otherwise the dup is dropped
ASP.NET (Request.QueryString["id"]) comma-concatenated ("1,2") GetValues returns both
ASP Classic comma-concatenated
Java Servlet (getParameter) first (1) getParameterValues returns both
Java Spring @RequestParam String first List<String> binds both
Node.js qs (Express default) array (["1","2"]) n/a
Node.js querystring (legacy) array n/a
Python Flask request.args.get first getlist returns both
Python Django request.GET['id'] last getlist returns both
Python urllib.parse.parse_qs list (["1","2"])
Ruby on Rails last params[:id] is the last; arrays via id[]=
Go net/http r.URL.Query().Get first ["id"] returns all
Perl CGI param("id") first in scalar, list in list context
nginx $arg_id first
Apache mod_rewrite %{QUERY_STRING} raw — passes both
AWS API Gateway → Lambda proxy last in queryStringParameters, all in multiValueQueryStringParameters
Cloudflare WAF inspects all values for rule match (generally)
AWS WAF inspects each occurrence
ModSecurity (CRS) inspects each — but anomaly score per rule

The exploitable pattern: WAF/proxy reads value A, app reads value B.

Read the full file on GitHub · 190 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 190 lines · 25 tokens per session scan A 8d686a182aa1

Subscribe to this mod's changes

hpp is a skill published in the GitHub repository PurpleAILAB/Decepticon (5,451 stars, last pushed 7d ago), licensed Apache-2.0. It adds 25 tokens to every session and 2,443 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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