# insecure-output-handling

> Claude/Codex skill by [@thejefflarson](https://omgskills.com/library/thejefflarson/index.md) · 20 stars · Updated 2026-07-31

Detects unsafe rendering or execution of LLM output that enables XSS, command injection, or second-order injection. Use when writing code that renders LLM output to a UI, executes LLM-generated code or shell commands, or passes LLM responses to downstream APIs or databases. Also invoke when displaying markdown or HTML from an LLM response.

Tags: llms, security, skills

## Install

```sh
git clone https://github.com/thejefflarson/soundcheck /tmp/soundcheck && ln -s /tmp/soundcheck/.claude/skills/insecure-output-handling ~/.claude/skills/insecure-output-handling
```

## From README

Insecure Output Handling Security Check (OWASP LLM02:2025) What this checks Protects against XSS, command injection, and second-order injection that arise when LLM output is treated as trusted. The model may produce malicious content through prompt injection or hallucination; downstream systems must sanitize it the same way they would sanitize raw user input. Vulnerable patterns LLM response assigned to a raw-HTML sink (innerHTML, dangerouslySetInnerHTML, v-html, server-side marksafe) without sanitization LLM-generated code or shell string passed to eval, exec, or a subprocess call with shell expansion enabled LLM output interpolated into a SQL or NoSQL query string instead of bound as a parameter LLM-produced markdown rendered to HTML without an allowlist-based sanitizer LLM response forwarded to a downstream API or webhook without re-validating against the destination's schema Fix immediately Flag the vulnerable code and explain the risk.

## Links

- HTML page: https://omgskills.com/library/thejefflarson/soundcheck/dot-claude/skills/insecure-output-handling/
- GitHub: https://github.com/thejefflarson/soundcheck
- Author: [@thejefflarson](https://omgskills.com/library/thejefflarson/index.md)

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