FrogPost: postMessage Security Testing Tool

by Nam Phong · July 1, 2025

FrogPost is a powerful Chrome extension for testing and analyzing the security of postMessage communications between iframes. It helps developers and security professionals identify vulnerabilities in message-handling implementations.

Security Testing

Key Features

Live monitor of cross-origin postMessage traffic
Automatic detection and analysis of message handlers
Static and runtime analysis for DOM-based vulnerabilities
Identification of missing origin checks and unsafe sinks
Targeted fuzzing of insecure handlers
Detailed security reports with payload suggestions
Passive Listener Detection
Callback Integration Fix
XSS Payload Library
POC Builder

Usage Highlights

Observe: Load any site with iframes. FrogPost captures postMessage exchanges.
Analyze: Click ▶ to begin handler analysis. Static fallback analysis is applied if runtime fails.
Trace: Use ✨ to trace data flows, detect DOM sinks, and generate security payloads.
Fuzz: Launch ? to test vulnerable endpoints using crafted fuzzing payloads.

Dashboard at a Glance

Per-Iframe Controls

▶ Play – Start handler detection and capture
✨ Trace – Static sink and flow analysis
? Report – Show results & Insights
? Launch – Begin fuzzing vulnerable handlers

?️ General Controls

Check All – Analyze all endpoints
Clear Messages – Reset state and logs
Export – Download captured messages
Refresh – Manually update messages
Debug Toggle – Verbose logging in console

? Message Controls

→ Send to Origin – Replay to sender
→ Send to Destination – Replay to receiver

Panels

Hosts Panel – Shows the main page and iframe connections
Messages Panel – Intercepted postMessage traffic
Security Report – DOM XSS and origin check findings

Install & Use

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