A guide to testing Server-Side Template Injection (SSTI), where user input is interpreted as template code on the server.

Use it with Jinja2, Twig, Freemarker, or Velocity applications when checking for code execution through templates.

It helps identify template features that let attackers read data or run commands through a template engine.

ssti — Skill for Claude Code by mohdhaji87/payloadsallthethings-skills

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add mohdhaji87/payloadsallthethings-skills --skill ssti

Clone the repo

git clone --depth 1 https://github.com/mohdhaji87/payloadsallthethings-skills

Made for: Claude Code.

Or install payloadsallthethings, the plugin that ships this one along with the rest of its 61 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/mohdhaji87/payloadsallthethings-skills/ssti/github.svg)](https://agentmods.dev/skills/mohdhaji87/payloadsallthethings-skills/ssti)

Your own site

<a href="https://agentmods.dev/skills/mohdhaji87/payloadsallthethings-skills/ssti"><img src="https://agentmods.dev/badge/skills/mohdhaji87/payloadsallthethings-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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/mohdhaji87/payloadsallthethings-skills/ssti"><img src="https://agentmods.dev/badge/skills/mohdhaji87/payloadsallthethings-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 1,993 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.

Origin unknown 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.

Model	Per session	Once invoked
Fable 5.1	$0.00029	$0.01993
Opus 5.5	$0.00012	$0.00797
Sonnet 5.5	$0.00006	$0.00399
Haiku 4.5	$0.00003	$0.00199

Measured 2mo ago against content hash b71eec25f48a, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

ssti 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 2mo 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.

{{this.push "return require('child_process').execSync('id');"}}

payloadsallthethings/skills/ssti/SKILL.md · 323 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

Read it on GitHub

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.

2mo ago First seen · 323 lines · 29 tokens per session scan A b71eec25f48a

Subscribe to this mod's changes

ssti is a skill published in the GitHub repository mohdhaji87/payloadsallthethings-skills (21 stars, last pushed 10mo ago), with no licence file. It adds 29 tokens to every session and 1,993 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-08-30.

Security Testing

ssti next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
sstimohdhaji87/payloadsallthethings-skills	Skill	21	10mo ago	none	A	29	Claude Code
imagegenopenai/codex	Skill	133k	yesterday	Apache-2.0	A	113	Codex
playwright-climicrosoft/playwright	Skill	99k	yesterday	Apache-2.0	A	19	Claude Code
local-ai-agentsmicrosoft/ai-agents-for-beginners	Skill	79k	4d ago	MIT	A	200	Claude Code, Codex
systematic-debuggingobra/superpowers	Skill	313k	3d ago	MIT	A	21	Claude Code
next-cache-components-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	95	Claude Code
next-partial-prefetching-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	103	Claude Code