HackSkills is an organized knowledge base of installable skills that gives AI agents practical security knowledge across areas such as web security, privilege escalation, reverse engineering, and digital forensics. It is intended for bug bounty work, penetration testing, CTF competitions, and authorized security research. The catalogue entries are the project's own master, category, and topic skills.
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 yaklang/hack-skills --skill ssti-server-side-template-injectiongit clone --depth 1 https://github.com/yaklang/hack-skillsWrote 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/yaklang/hack-skills/ssti-server-side-template-injection)<a href="https://agentmods.dev/skills/yaklang/hack-skills/ssti-server-side-template-injection"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/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/yaklang/hack-skills/ssti-server-side-template-injection"><img src="https://agentmods.dev/badge/skills/yaklang/hack-skills/ssti-server-side-template-injection.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket fail
- Snyk fail
- NVIDIA SkillSpector warn
SkillSpector: 3 findings, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Privilege Escalation · line 224 Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
- high Privilege Escalation · line 337 Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
- high Privilege Escalation · line 278 Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
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 6d 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): Copies of this mod
3 near-identical copies found in the catalogue:
- ssti-server-side-template-injection — 100% identical, 0 lines differ
- ssti-server-side-template-injection — 100% identical, 0 lines differ
- ssti-server-side-template-injection — 98% identical, 4 lines differ
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.
- 6d 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 yaklang/hack-skills (2,133 stars, last pushed 2mo ago), licensed MIT. 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). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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