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.
npx skills add JustineDevs/premortem --skill ssti-server-side-template-injectiongit clone --depth 1 https://github.com/JustineDevs/premortemWrote 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/justinedevs/premortem/ssti-server-side-template-injection)<a href="https://agentmods.dev/skills/justinedevs/premortem/ssti-server-side-template-injection"><img src="https://agentmods.dev/badge/skills/justinedevs/premortem/ssti-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/justinedevs/premortem/ssti-server-side-template-injection"><img src="https://agentmods.dev/badge/skills/justinedevs/premortem/ssti-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 | $0.00036 | $0.03301 |
| Opus 5 | $0.00018 | $0.01650 |
| Sonnet 5 | $0.00007 | $0.00660 |
| Haiku 4.5 | $0.00004 | $0.00330 |
Grade B, and why
ssti-server-side-template-injection scanned grade B 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 9d 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.
Reaches for credential filesmediumPrivilege escalation
SSH keys, cloud credentials, git-credentials, .npmrc, /etc/shadow: reading these is how a config file becomes a credential leak.
3. `cat ~/.aws/credentials` — cloud credentials Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
Runs shell commandslowCapability
Expected in a hook, worth knowing in a rule or an instructions file.
# Find subprocess.Popen index (usually around 258-270, varies by Python version): This is a copy
100% identical to ssti-server-side-template-injection — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 345 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: Server-Side Template Injection (SSTI) — Expert Attack Playbook
AI LOAD INSTRUCTION: Expert SSTI techniques. Covers polyglot detection probes, engine fingerprinting, Jinja2/FreeMarker/Twig/ERB RCE chains, client-side Angular SSTI, and bypass techniques. Base models often miss sandbox escape MRO chains and non-Jinja2 engines. For PHP CMS template eval, Jira SSTI, Confluence OGNL, and Spring Cloud Gateway SpEL, load the companion SCENARIOS.md.
0. RELATED ROUTING
Before using full engine-specific exploitation, you can first load:
- First use the polyglot probe sequence at the top of this file for low-noise fingerprinting
- expression-language-injection when
${7*7}or%{7*7}resolves in Java (SpEL/OGNL) — different attack surface from template engines
Extended Scenarios
Also load SCENARIOS.md when you need:
- Maccms 8.x PHP template
eval—{if-A:phpinfo()}{endif-A}invod-search, base64 bypass for webshell write - Jira CVE-2019-11581 — "Contact Administrators" form → Velocity template injection → command output in admin email
- Spring Cloud Gateway SpEL (CVE-2022-22947) — actuator route injection with
StreamUtils.copyToByteArrayfor output capture - Struts2 OGNL S2-045 (CVE-2017-5638) — Content-Type header OGNL injection with
_memberAccess/OgnlUtilblacklist clear - Confluence OGNL CVE-2021-26084 —
createpage-entervariables.actionwith\u0027unicode bypass - SSTI vs EL injection disambiguation guide
- Additional template engines: ASP.NET Razor, Elixir EEx, PHP Smarty/Latte/Blade, JS Pug/Handlebars/Nunjucks/EJS/Lodash + universal detection + blind SSTI + Flask PIN calculation
SCENARIOS.md reference (§7–§11): For expanded payloads and engine-specific notes on Razor, EEx/LEEx/HEEx, PHP stacks, JavaScript template engines, the universal polyglot probe, mathematical fingerprinting, blind SSTI (boolean / time / OOB), and Flask debug PIN prerequisites, see SCENARIOS.md. This skill keeps a short checklist in §13–§15.
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.
- 9d ago First seen · 345 lines · 36 tokens per session scan B f03a7bd241d7
ssti-server-side-template-injection is a skill published in the GitHub repository JustineDevs/premortem (2 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 36 tokens to every session and 3,301 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it B with 2 findings (reaches for credential files, runs shell commands). It is 100% identical to ssti-server-side-template-injection, differing in 0 lines, and is treated as a copy.
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