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Why this module exists. Input validation and output encoding are the universal defences against the OWASP Top 10 of injection vulnerabilities — SQL injection, XSS, command injection, LDAP injection, XXE. Every framework provides them; every developer claims to use them; many still ship vulnerable code. This module covers the principles and the language-specific patterns.
Why this module exists. The single highest-leverage developer education is the principle “structure separates code from data.” Input validation and output encoding operationalise that principle. This module is the practitioner’s reference.
The principle — structure separates code from data
Injection vulnerabilities exist because data is interpreted as code by some downstream parser — SQL parser, HTML parser, shell parser, XML parser, LDAP parser. The defence is two-layered:
- Input validation: reject data that does not match expected structure.
- Output encoding: render data in a way the downstream parser cannot interpret as structure.
Both are needed. Validation alone misses; encoding alone is brittle.
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