# Account Enumeration

> Detects authentication and registration endpoints that reveal whether a username or email exists, enabling targeted attacks.

- Skill: `zakirkun/account-enumeration` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add zakirkun/account-enumeration`
- Raw SKILL.md: https://api.skillmd.com/api/skills/zakirkun/account-enumeration/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Productivity
- Author: zakirkun (https://skillmd.com/u/zakirkun)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/zakirkun/account-enumeration

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# Account Enumeration

## Overview
Applications that return different responses for valid vs invalid usernames allow attackers to enumerate valid accounts for:
- Targeted phishing campaigns
- Credential stuffing (knowing which accounts exist)
- Social engineering targeting known employees

## Detection Strategy
Look for error messages that distinguish "wrong password" from "user not found".

## Remediation
- Return identical error messages regardless of whether username exists
- Use constant-time comparison to prevent timing-based enumeration
- Implement CAPTCHA after multiple failed attempts