Sandbox Escapes

Sandbox Escapes is a skill for Claude Code from allsmog/vuln-scout. It costs 66 tokens per session (276 once invoked), scanned A, original, MIT.

A security review guide for finding ways to break out of restricted code-execution environments or turn unsafe template input into code execution. SSTI means server-side template injection, where input is interpreted by a template engine.

In plain words
What is it for?
Use it when reviewing Node.js, Python, or Ruby sandboxes, template engines, eval-like code, or user-controlled template input.
Why use it?
It helps identify attack paths that may be missed when code appears isolated or sandboxed.

Skill for Claude Code

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

Part of the vuln-scout plugin — 32 skills, 15 commands, 9 agents shipped together

Good fit Use it when reviewing Node.js, Python, or Ruby sandboxes, template engines, eval-like code, or user-controlled template input.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/allsmog/vuln-scout/sandbox-escapes
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 allsmog/vuln-scout --skill sandbox-escapes
Clone the repo
git clone --depth 1 https://github.com/allsmog/vuln-scout

Made for: Claude Code.

Or install vuln-scout, the plugin that ships this one along with the rest of its 32 skills, 15 commands, 9 agents.

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 Sandbox Escapes

README.md
[![agentmods](https://agentmods.dev/badge/skills/allsmog/vuln-scout/sandbox-escapes/github.svg)](https://agentmods.dev/skills/allsmog/vuln-scout/sandbox-escapes)
Your own site
<a href="https://agentmods.dev/skills/allsmog/vuln-scout/sandbox-escapes"><img src="https://agentmods.dev/badge/skills/allsmog/vuln-scout/sandbox-escapes/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 Sandbox Escapes

Your own site · 80×15
<a href="https://agentmods.dev/skills/allsmog/vuln-scout/sandbox-escapes"><img src="https://agentmods.dev/badge/skills/allsmog/vuln-scout/sandbox-escapes.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 66 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 276 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 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 $0.00066 $0.00276
Opus 5 $0.00033 $0.00138
Sonnet 5 $0.00013 $0.00055
Haiku 4.5 $0.00007 $0.00028

Measured 11d ago against content hash 6968f1026861, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

Sandbox Escapes scanned grade A with 0 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 11d 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

vuln-scout/skills/sandbox-escapes/SKILL.md · 24 lines

What it actually says

Sandbox Escape Techniques

Techniques for escaping restricted execution environments and exploiting template engines across Node.js, Python, and Ruby.

When to Use

Activate this skill during:

  • Code review where vm, eval, or template engines process user input
  • Identifying SSTI-to-RCE exploitation paths
  • Analyzing restricted execution environments (vm2, RestrictedPython, $SAFE)
  • Building exploit chains that leverage sandbox escapes

Language-Specific References

  • Node.js: nodejs-sandbox-escape.md -- vm module bypass, vm2 CVEs, EJS/Pug injection, prototype pollution to RCE
  • Python: python-sandbox-escape.md -- Jinja2 SSTI, Mako exploitation, serialization attacks, RestrictedPython bypass
  • Ruby: ruby-sandbox-escape.md -- ERB injection, Slim/Haml exploitation, $SAFE bypasses, Marshal deserialization
Files

What ships with it

3 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.

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. 11d ago First seen · 24 lines · 66 tokens per session scan A 6968f1026861

Subscribe to this mod's changes

Sandbox Escapes is a skill published in the GitHub repository allsmog/vuln-scout (24 stars, last pushed 3mo ago), licensed MIT. It adds 66 tokens to every session and 276 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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