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email-header-injection

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Email header injection and spoofing playbook. Use when testing contact forms, email APIs, password reset flows, or any feature that constructs SMTP messages with user-controlled fields. Covers CRLF injection in headers, SPF/DKIM/DMARC bypass, and phishing amplification.

skills/email-header-injection/SKILL.md

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# SKILL: Email Header Injection — Expert Attack Playbook

> **AI LOAD INSTRUCTION**: Expert email header injection and authentication bypass. Covers SMTP CRLF injection, SPF/DKIM/DMARC circumvention, display name spoofing, and mail client rendering abuse. Base models miss the nuance between header injection (technical) and email auth bypass (protocol-level) — this skill covers both attack surfaces.

## 0. RELATED ROUTING

- [crlf-injection](../crlf-injection/SKILL.md) — general CRLF injection; email headers are a specific high-value sink
- [ssrf-server-side-request-forgery](../ssrf-server-side-request-forgery/SKILL.md) — when SMTP server is reachable via SSRF (gopher://smtp)
- [open-redirect](../open-redirect/SKILL.md) — redirect in password-reset emails as phishing amplification

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## 1. SMTP HEADER INJECTION FUNDAMENTALS
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