report-writing skill

by elementalsouls·elementalsouls/Claude-BugHunter·4.7k stars·MIT

Bug bounty report writing for H1/Bugcrowd/Intigriti/Immunefi — report templates, human tone guidelines, impact-first writing, CVSS 3.1 scoring, title formula, impact statement formula, severity decision guide, downgrade counters, pre-submit checklist. Validation gates and the submittability/always-rejected decision are owned by triage-validation; this skill owns the written report itself (templates, tone, formulas). Use after validating a finding and before submitting. Never use "could potentially" — prove it or don't report.

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Is the report-writing skill safe?

Clean: nothing in its files matched our rules. We read 1 file in the folder on 2026-09-28.

No findings.

Install the report-writing skill

A skill is a folder. Copy it into your agent's skills folder and the agent loads it when the task matches its description.

git clone --depth 1 https://github.com/elementalsouls/Claude-BugHunter.git /tmp/Claude-BugHunter
mkdir -p ~/.claude/skills
cp -r /tmp/Claude-BugHunter/skills/report-writing ~/.claude/skills/report-writing

available in every project

In the Claude apps, zip the folder and upload it from the Skills settings. The folder on GitHub

The instructions your agent would load

SKILL.md as published, without the frontmatter. Read it on GitHub

REPORT WRITING

Impact-first. Human tone. No theoretical language. Triagers are people.

THE MOST IMPORTANT RULE

Never use "could potentially" or "could be used to" or "may allow".

Either it does the thing or it doesn't. If you haven't proved it, don't claim it.

BAD:  "This vulnerability could potentially allow an attacker to access user data."
GOOD: "An attacker can access any user's order history by changing the user_id
       parameter to the target user's ID. I confirmed this using two test accounts:
       attacker@test.com (ID 123) successfully retrieved victim@test.com (ID 456)
       orders, including their shipping address and payment method last 4 digits."

TITLE FORMULA

[Bug Class] in [Exact Endpoint/Feature] allows [attacker role] to [impact] [victim scope]

Good titles (specific, impact-first):

IDOR in /api/v2/invoices/{id} allows authenticated user to read any customer's invoice data
Missing auth on POST /api/admin/users allows unauthenticated attacker to create admin accounts
Stored XSS in profile bio field executes in admin panel — allows privilege escalation
SSRF via image import URL parameter reaches AWS EC2 metadata service
Race condition in coupon redemption allows same code to be used unlimited times

Bad titles (vague, useless to triager):

IDOR vulnerability found
Broken access control
XSS in user input
Security issue in API
Unauthorized access to user data

HACKERONE REPORT TEMPLATE

## Summary

[One paragraph: what the bug is, where it is, what an attacker can do. Be specific.
Include: endpoint, method, parameter, data exposed, required access level.]

Example: "The `/api/users/{user_id}/orders` endpoint does not verify that the
authenticated user owns the requested user_id. An attacker can enumerate any
user's order history, including PII (email, address, phone) and purchase history,
by incrementing the user_id parameter. No privileges beyond a standard free
account are required."

## Vulnerability Details

**Vulnerability Type:** IDOR / Broken Object Level Authorization
**CVSS 3.1 Score:** 6.5 (Medium) — AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
**Affected Endpoint:** GET /api/users/{user_id}/orders

## Steps to Reproduce

**Environment:**
- Attacker account: attacker@test.com, user_id = 123
- Victim account: victim@test.com, user_id = 456
- Target: https://target.com

**Steps:**

1. Log in as attacker@test.com, obtain Bearer token

2. Send the following request:

GET /api/users/456/orders HTTP/1.1 Host: target.com Authorization: Bearer ATTACKERTOKENHERE

3. Observe response:

{ "orders": [ {"id": 789, "items": [...], "email": "victim@test.com", "address": "123 Main St..."} ] }

The response contains victim's full order history and PII despite being requested
by a different user.

## Impact

An authenticated attacker can enumerate all user orders by iterating user_id values.
This exposes: full name, email, shipping address, purchase history, and payment
method (last 4). With ~100K users, this represents a mass PII breach affecting
all registered users. Exploitation requires only a free account and takes minutes
with a simple loop.

## Recommended Fix

Add server-side ownership verification:

if order.userid != currentuser.id: raise Forbidden()

## Supporting Materials

[Screenshot showing attacker's session returning victim's order data]
[Video walkthrough if available]

BUGCROWD REPORT TEMPLATE

# [IDOR] User order history accessible without authorization via /api/users/{id}/orders

**VRT Category:** Broken Access Control > IDOR > P2

## Description

[Same impact-first paragraph as HackerOne summary]

## Steps to Reproduce

[Same structured steps — exact HTTP requests, exact responses]

## Proof of Concept

[Screenshot/video showing the actual impact]

## Expected vs Actual Behavior

**Expected:** 403 Forbidden when user_id does not match authenticated user
**Actual:** 200 OK with victim's full order data

## Severity Justification

P2 (High) — Direct read access to other users' PII. Affects all user accounts.
No user interaction required. Exploitable by any authenticated user.
Automated enumeration could exfil all [N] user records in minutes.

## Remediation

Add ownership verification: `if order.user_id != current_user.id: raise 403`

INTIGRITI REPORT TEMPLATE

# [Bug Class]: [Exact Impact] in [Endpoint/Feature]

## Description

[Impact-first paragraph. Start with what an attacker can do, not with how you found it.
Include: endpoint, method, parameter, data exposed, required privileges.]

## Steps to Reproduce

**Environment:**
- Attacker: email=attacker@test.com (standard account, no special role)
- Victim: email=victim@test.com
- Tested: [date]

**Reproduction steps:**

1. [Login as attacker / visit URL / send request]

2. Send the following HTTP request:

\```http
METHOD /endpoint HTTP/1.1
Host: target.com
Authorization: Bearer ATTACKER_TOKEN
Content-Type: application/json

{"param": "victim_id_here"}
\```

3. Observe response contains victim's private data:

\```json
{"email": "victim@test.com", "address": "123 Main St", ...}
\```

## Impact

[Specific, quantified impact. What data, how many users, what can attacker do.]

CVSS 3.1 Score: X.X ([Severity]) — AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

## Remediation

[1-3 sentence concrete fix. Include code if helpful.]

## Attachments

[Screenshot or Loom video showing the impact — Intigriti triagers prefer video for complex bugs]

Intigriti-specific notes:

Title format: [Bug Class]: [One-line impact] (no formula required, but keep it specific)
Severity is set by you: Critical/High/Medium/Low/Exceptional
CVSS 3.1 is standard (CVSS 4.0 also accepted on newer programs)
PoC video is valued much more than screenshot alone — record with Loom
Safe harbor: Intigriti enforces it, be comfortable going slightly aggressive with testing

IMMUNEFI REPORT TEMPLATE

# [Bug Class] — [Protocol Name] — [Severity]

## Summary

[One paragraph with: root cause, affected function, economic impact, attack cost.
Include numbers where possible: "attacker can drain $X in Y transactions."]

## Vulnerability Details

**Contract:** `VulnerableContract.sol`
**Function:** `claimRedemption()`
**Bug Class:** Accounting State Desynchronization
**Severity:** Critical

### Root Cause

[Exact code snippet showing the vulnerable code with comments]

## Proof of Concept

// SPDX-License-Identifier: MIT pragma solidity ^0.8.0; // Foundry PoC — run: forge test --match-test test_exploit -vvvv

contract ExploitTest is Test { // ... full working exploit }

## Impact

[Quantified: "Attacker can drain X% of TVL = $Y at current rates.
Requires $Z gas. Attack is repeatable."]

## Recommended Fix

[Specific code change with before/after]

CVSS 3.1 QUICK SCORING

Formula

CVSS = f(AV, AC, PR, UI, S, C, I, A)

Metric Quick Picks

Typical Scores by Bug Class

SEVERITY DECISION GUIDE

Critical (P1)

Full account takeover of any user without interaction
Remote code execution
SQLi with ability to dump/modify entire DB
Auth bypass to admin panel
SSRF to cloud metadata → IAM credentials exfil

High (P2)

Mass PII exposure (email, phone, SSN, payment data)
Privilege escalation from user to admin
SSRF reaching internal services (data returned)
Stored XSS executing for all users of sensitive feature
Payment bypass / financial loss without limit

Medium (P3)

IDOR on specific user's non-critical data
XSS on low-sensitivity page requiring victim interaction
CSRF on important but non-critical action
Rate limit bypass on OTP (with effort demonstrated)

Low (P4)

Information disclosure (non-sensitive, no PII)
Clickjacking on sensitive action WITH working PoC
CORS on limited data

SEVERITY SELF-ASSESSMENT

Each YES raises severity:

1. Exposes PII / health / financial data of other users?        → +1 severity
2. Allows account takeover or privilege escalation?             → +2 severity
3. Requires ZERO user interaction from victim?                  → +1 severity
4. Affects ALL users (not specific condition)?                  → +1 severity
5. Remotely exploitable with no internal network access?        → baseline for High+

DOWNGRADE COUNTERS

THE 60-SECOND PRE-SUBMIT CHECKLIST

[ ] Title follows formula: [Class] in [endpoint] allows [actor] to [impact]
[ ] First sentence states exact impact in plain English
[ ] Steps to Reproduce has exact HTTP request (copy-paste ready)
[ ] Response showing the bug is included (screenshot or JSON body)
[ ] Two test accounts used — not just one account testing itself
[ ] CVSS score calculated and included
[ ] Recommended fix is 1-2 sentences (not a lecture)
[ ] No typos in endpoint paths or parameter names
[ ] Report is < 600 words — triagers skim long reports
[ ] Severity claimed matches impact described — don't overclaim
[ ] Never used "could potentially" or "may allow"
[ ] PoC is reproducible by triager from a fresh state

CVSS 4.0 QUICK REFERENCE (newer programs)

CVSS 4.0 replaced CVSS 3.1 in November 2023. Some newer programs require it.

Key Differences from CVSS 3.1

CVSS 4.0 Score Examples

Quick CVSS 4.0 Calculator

Use: https://www.first.org/cvss/calculator/4.0
Key fields:
  VC/VI/VA = Vulnerable System Confidentiality/Integrity/Availability
  SC/SI/SA = Subsequent System (downstream impact)
  AT = None (no special condition) | Present (race/specific config needed)
  UI = None | Passive (victim visits URL) | Active (victim takes explicit action)

Practical rule: If program uses CVSS 4.0 and you don't know the vector, use the calculator and include the full string starting with CVSS:4.0/AV:.... Programs cannot dispute a valid vector string.

HUMAN TONE GUIDELINES

Write to a person, not a system:

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