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.
git clone --depth 1 https://github.com/akashrpatil/awesome-offensive-security-skillsnpx agentmods add skills/akashrpatil/awesome-offensive-security-skills/server-side-template-injectionWrote 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.
[](https://agentmods.dev/skills/akashrpatil/awesome-offensive-security-skills/server-side-template-injection)<a href="https://agentmods.dev/skills/akashrpatil/awesome-offensive-security-skills/server-side-template-injection"><img src="https://agentmods.dev/badge/skills/akashrpatil/awesome-offensive-security-skills/server-side-template-injection/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.
<a href="https://agentmods.dev/skills/akashrpatil/awesome-offensive-security-skills/server-side-template-injection"><img src="https://agentmods.dev/badge/skills/akashrpatil/awesome-offensive-security-skills/server-side-template-injection.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00084 | $0.02038 |
| Opus 5 | $0.00042 | $0.01019 |
| Sonnet 5 | $0.00017 | $0.00408 |
| Haiku 4.5 | $0.00008 | $0.00204 |
Grade A, and why
server-side-template-injection scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Runs shell commandslowCapability
Expected in a hook, worth knowing in a rule or an instructions file.
# Search the output for classes capable of executing commands, such as `subprocess.Popen`, `os._wrap_close`, or `importlib`. How it starts
The opening of the file, as written. The whole thing — 182 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Server-Side Template Injection (SSTI)
When to Use
- When discovering input fields (e.g., Usernames, Email Templates, URL parameters) that are directly rendered or reflected on the corresponding web page without sanitization.
- When XSS (Cross-Site Scripting) payloads are blocked or escaped, but the server appears to be interpreting special bracket characters (
{{ }},${ },<% %>). - When attempting to escalate a simple input reflection bug into full Remote Code Execution (RCE) on the server.
Prerequisites
- Authorized scope and target URLs from bug bounty program
- Burp Suite Professional (or Community) configured with browser proxy
- Familiarity with OWASP Top 10 and common web vulnerability classes
- SecLists wordlists for fuzzing and enumeration
Workflow
Phase 1: Detection and Identification
# Concept: If an application unsafely passes user input into a template rendering engine,
# it will evaluate mathematical expressions wrapped in template syntax.
# 1. Probe the application with standard template tags
{{7*7}}
${7*7}
<%= 7*7 %>
${{7*7}}
#{7*7}
*{7*7}
# 2. Analyze the response
# If the application reflects verbatim: "{{7*7}}" -> Not vulnerable, or wrong tag.
# If the application reflects: "49" -> CRITICAL! SSTI exists. The server evaluated the math.
# If the application throws an Error: The stack trace often reveals the exact engine (e.g., "Jinja2 Exception", "Twig Error").
Phase 2: Engine Mapping
# Once mathematical evaluation is proven, you must determine WHICH template engine is running,
# as specific payloads vary drastically between Python, Java, Ruby, and PHP engines.
# PortSwigger SSTI Decision Tree:
# Input: {{7*'7'}}
# - If output is 49 -> Looks like Twig (PHP)
# - If output is 7777777 -> Looks like Jinja2 (Python) or Nunjucks (Node)
# - If output is error -> Try Java/Ruby syntaxes.
# Input: ${7/0}
# Java engines (Freemarker, Velocity) will throw specific arithmetic exceptions.
Phase 3: Context Escaping and Sandbox Evasion
What ships with it
2 files 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.
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.
- 7d ago First seen · 182 lines · 84 tokens per session scan A ae6985abe306
server-side-template-injection 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 84 tokens to every session and 2,038 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 1 finding (runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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