Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/JustineDevs/premortemnpx agentmods add skills/justinedevs/premortem/authbypass-authentication-flawsWrote 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.
[](https://agentmods.dev/skills/justinedevs/premortem/authbypass-authentication-flaws)<a href="https://agentmods.dev/skills/justinedevs/premortem/authbypass-authentication-flaws"><img src="https://agentmods.dev/badge/skills/justinedevs/premortem/authbypass-authentication-flaws/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.
<a href="https://agentmods.dev/skills/justinedevs/premortem/authbypass-authentication-flaws"><img src="https://agentmods.dev/badge/skills/justinedevs/premortem/authbypass-authentication-flaws.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00043 | $0.03830 |
| Opus 5 | $0.00022 | $0.01915 |
| Sonnet 5 | $0.00009 | $0.00766 |
| Haiku 4.5 | $0.00004 | $0.00383 |
Grade A, and why
authbypass-authentication-flaws scanned grade A with 0 findings 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 9d 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.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
100% identical to authbypass-authentication-flaws — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 442 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: Authentication Bypass — Expert Attack Playbook
AI LOAD INSTRUCTION: Expert authentication bypass techniques. Covers SQL injection-based login bypass, password reset flaws, token predictability, account enumeration, brute force bypass, and multi-factor auth bypass. Distinct from JWT/OAuth (covered in ../jwt-oauth-token-attacks/SKILL.md). Focus on the login mechanism itself.
0. AUTHORIZED CREDENTIAL TEST PLANNING
After reducing routing entries, default credentials, username variants, port focus, and wordlist sizing are handled here in one place.
Service-first tiny sets
| Service Type | First Usernames | First Passwords |
|---|---|---|
| phpMyAdmin | root, admin |
empty, root, phpmyadmin, admin |
| FTP | ftp, admin, test |
empty, ftp, admin, 123456 |
| SSH | root, admin, service account names |
root, admin, seasonal variants |
| MySQL | root, mysql |
empty, root, mysql |
| Tomcat / Java admin | tomcat, admin, manager |
tomcat, admin, s3cret |
| WebLogic | weblogic, admin |
weblogic, welcome1, admin |
Username classes
| Class | Examples |
|---|---|
| Generic admins | admin, administrator, root, test, guest |
| Support / ops | dev, ops, sysadmin, service, backup |
| Name-based | firstname, lastname, f.lastname, first.last |
| Mail-derived | left side of corporate email formats |
| Product-based | tomcat, weblogic, jenkins, gitlab |
Wordlist sizing and port focus
| Scenario | Preferred Size | Why |
|---|---|---|
| Default admin panel | 5 to 50 passwords | Defaults beat giant lists here |
| Internal service with known product | vendor-specific small set | Better signal than generic lists |
| Consumer login with weak controls | Top 20 or Top 100 | Fast verification |
| Rate-limited login | tiny list + header/rotation strategy | Preserve attempts |
| Offline hash cracking | large dictionaries | Online brute rules do not apply |
Prioritize common ports and service surfaces: 80/443/8080/8443 admin panels, 22 SSH, 21 FTP, and 3306/5432/6379/27017 data or management services.
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.
- 9d ago First seen · 442 lines · 43 tokens per session scan A e930a9b50792
authbypass-authentication-flaws is a skill published in the GitHub repository JustineDevs/premortem (2 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 43 tokens to every session and 3,830 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to authbypass-authentication-flaws, differing in 0 lines, and is treated as a copy.
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