# Insecure PostMessage Configuration

> Detects careless use of the HTML5 Web Messaging API (postMessage), such as sending messages to the generic '*' origin.

- Skill: `zakirkun/insecure-postmessage-configuration` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add zakirkun/insecure-postmessage-configuration`
- Raw SKILL.md: https://api.skillmd.com/api/skills/zakirkun/insecure-postmessage-configuration/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: zakirkun (https://skillmd.com/u/zakirkun)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/zakirkun/insecure-postmessage-configuration

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# Insecure PostMessage Configuration

## Overview
Detects careless use of the HTML5 Web Messaging API (postMessage), such as sending messages to the generic '*' origin.

## Remediation
Always specify the exact target origin in window.postMessage(). When receiving messages, rigorously verify event.origin.