input-validation-and-sanitization
Use this skill when implementing any endpoint, form handler, CLI tool, or function that accepts external input. Validate and sanitize all untrusted data before processing — never assume input is safe.
Source facts
- Repository
- aiming-lab/MetaClaw
- Last source activity
- March 10, 2026 at 18:04
- Detected SKILL.md language
- English
- Stars
- 3,464
- Forks
- 453
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- input-validation-and-sanitization
- description
- Use this skill when implementing any endpoint, form handler, CLI tool, or function that accepts external input. Validate and sanitize all untrusted data before processing — never assume input is safe.
- category
- security
# Input Validation and Sanitization
**Validation principles:**
- Validate at the system boundary (API layer, form handler) — not deep in business logic.
- Validate type, range, length, and format explicitly.
- Reject unexpected input by default (allowlist > denylist).
**SQL injection prevention:** Always use parameterized queries or an ORM.
**XSS prevention:** Escape HTML output; use Content-Security-Policy headers; avoid `innerHTML` with user data.
**Path traversal prevention:** Resolve paths to canonical form and verify they are under the expected directory.
```python
import os
base = '/allowed/dir'
canonical = os.path.realpath(os.path.join(base, user_input))
assert canonical.startswith(base + os.sep)
```
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