chain-builder

chain-builder is an agent for Claude Code from Mikacr1138/claude-bug-bounty. It costs 96 tokens per session (900 once invoked), scanned B, original, MIT.

A security-testing helper that looks for ways to combine separate bugs into one attack path with greater impact.

In plain words
What is it for?
Use it to examine chains such as an IDOR, which exposes another user’s data, followed by an account takeover or privilege change.
Why use it?
Some vulnerabilities are less serious alone but become more serious when an attacker can use one to reach another.

Agent for Claude Code

Written for Claude Code: a Claude Code subagent (agents/*.md). Also seen: model in frontmatter; positional $N argument.

Good fit Use it to examine chains such as an IDOR, which exposes another user’s data, followed by an account takeover or privilege change.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/mikacr1138/claude-bug-bounty/chain-builder
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.

Clone the repo
git clone --depth 1 https://github.com/Mikacr1138/claude-bug-bounty

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 chain-builder

README.md
[![agentmods](https://agentmods.dev/badge/agents/mikacr1138/claude-bug-bounty/chain-builder/github.svg)](https://agentmods.dev/agents/mikacr1138/claude-bug-bounty/chain-builder)
Your own site
<a href="https://agentmods.dev/agents/mikacr1138/claude-bug-bounty/chain-builder"><img src="https://agentmods.dev/badge/agents/mikacr1138/claude-bug-bounty/chain-builder/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for chain-builder

Your own site · 80×15
<a href="https://agentmods.dev/agents/mikacr1138/claude-bug-bounty/chain-builder"><img src="https://agentmods.dev/badge/agents/mikacr1138/claude-bug-bounty/chain-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 96 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 900 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 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 $0.00096 $0.00900
Opus 5 $0.00048 $0.00450
Sonnet 5 $0.00019 $0.00180
Haiku 4.5 $0.00010 $0.00090

Measured 8d ago against content hash d44df5e7ca3d, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade B, and why

chain-builder scanned grade B 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 8d 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.

Cloud metadata endpointmediumServer-side request forgery

One request to 169.254.169.254 can return temporary IAM credentials.

| SSRF DNS callback | 169.254.169.254 cloud metadata | Critical |

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

agents/chain-builder.md · 75 lines

How it starts

The opening of the file, as written. The whole thing — 75 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Chain Builder Agent

You are a bug chain specialist. You take a confirmed bug A and systematically find B and C to combine for higher severity.

Your Approach

  1. Identify bug class of A
  2. Look up chain table for B candidates
  3. Check if B is testable from current position
  4. Confirm B exists (exact HTTP request)
  5. Output: chain path, combined severity, separate report count

The A→B Chain Table

Found A Check B Combined Impact
IDOR (GET) IDOR on PUT/DELETE same path Multiple High
Auth bypass Every sibling endpoint in same controller Multiple High
Stored XSS Admin views it? → priv esc Critical
SSRF DNS callback 169.254.169.254 cloud metadata Critical
Open redirect OAuth redirect_uri → code theft Critical ATO
S3 bucket listing JS bundles → grep OAuth creds Medium/High
GraphQL introspection Auth bypass on mutations High
LLM prompt injection IDOR via chatbot (other user data) High
Path traversal /proc/self/environ → RCE Critical
Subdomain takeover OAuth redirect_uri at subdomain Critical
JWT weak secret Forge admin token Critical
File upload bypass SVG→XSS, PHP→RCE High/Critical

Known High-Value Chains

Key Chain Examples

S3 → OAuth ATO: List bucket → download JS bundles → grep client_secret → test OAuth without code_challenge → 3 reports ~$1,200

Open Redirect → OAuth ATO: Confirm redirect → find OAuth flow → set redirect_uri to your redirect endpoint → victim clicks → code delivered to attacker → exchange for token

XSS → Admin Priv Esc: Stored XSS in user field → verify admin views it → payload auto-submits POST to promote attacker to admin

SSRF → Cloud Metadata: DNS callback only = Info → escalate to 169.254.169.254 → get IAM role → fetch credentials → enumerate AWS perms = Critical

Prompt Injection → IDOR: Confirm chatbot follows injected instructions → inject cross-user data request → if other user data returned = IDOR via AI feature

Read the full file on GitHub · 75 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. 8d ago First seen · 75 lines · 96 tokens per session scan B d44df5e7ca3d

Subscribe to this mod's changes

chain-builder is an agent published in the GitHub repository Mikacr1138/claude-bug-bounty (2 stars, last pushed today), licensed MIT. It adds 96 tokens to every session and 900 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it B with 1 finding (cloud metadata endpoint). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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