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hunt-ssti

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Hunt server-side template injection (SSTI) across Jinja2 (Flask/Django), Twig (Symfony), Freemarker (Java), ERB (Rails), Spring, Velocity, Mako, Thymeleaf, Smarty. Detection probes use double-curly and dollar-curly math expressions evaluated server-side. Once an engine is fingerprinted, escalate to RCE via the engine-specific class-walker, callback-registrar, or Execute-utility patterns documented in disclosed reports. Detection patterns: error messages reveal engine, blank or numeric eval reveals expression mode. Targets: email templates, PDF/report generators, CMS preview features, error pages with user input. Use when hunting RCE via template rendering, when content shows engine fingerprints, when finding endpoints that compose strings with user input before render.

skills/hunt-ssti/SKILL.md

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Nov 11, 2026

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Nov 10, 2026
License
MIT

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## Autonomous Testing Priority

**Escalate straight to RCE — don't stop at arithmetic detection.**

Arithmetic probes (`{{7*7}}→49`) confirm the injection point but are not proof of impact. The real goal is OS command execution. Arithmetic detection also fails silently when the app echoes the input back (e.g. inside an HTML attribute like `<input value="{{7*7}}">`), producing a false negative even when injection exists.

**Order of attack:**
1. **Try Jinja2 RCE first** (covers Python/Flask — the most common stack in modern web apps):
   ```
   {{config.__class__.__init__.__globals__['os'].popen('id').read()}}
   ```
2. **If the endpoint is a traditional web form**, send as form-encoded body — NOT JSON:
   ```
   Content-Type: application/x-www-form-urlencoded
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