# MessPostage

> Notify user of postMessage messages and event handlers. This is helpful during debugging or security testing of a web application.

Canonical page: [https://chrome-stats.com/d/messpostage](https://chrome-stats.com/d/messpostage)

## Overview

- **ID:** `messpostage`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** Sjoerd Langkemper
- **Category:** web-development,other
- **Daily users:** 93
- **Weekly downloads:** 3
- **Rating:** 5.00 / 5 (2 ratings)
- **Version:** 0.0.8resigned1
- **Last updated:** 2024-04-26
- **First published:** 2018-08-28
- **Size:** 27 KB
- **Data as of:** 2026-09-08
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/messpostage/)
- **Website:** [https://github.com/Sjord/messpostage](https://github.com/Sjord/messpostage)

## Description

MessPostage is a Chrome extension designed to notify users when postMessage communications occur between windows or iframes in a web application. This tool is especially useful for developers and security testers who need to track and debug message passing events typically handled by the postMessage API. By providing real-time notifications of messages and associated event handlers, MessPostage helps improve the visibility into cross-origin communication, enhancing both debugging efficiency and security analysis during development.

With MessPostage, users gain an easy-to-use interface that alerts them whenever a postMessage event is triggered. This extension is essential for web developers looking to monitor and verify message exchanges between different domains within their apps, ensuring proper data flow and reducing vulnerabilities.

## Rankings

- #11,978 — Overall

## Permissions and access

### Permissions

- `webNavigation`

### Content script matches

- `<all_urls>`

## Safety

- **Risk impact:** High risk impact
- **Risk likelihood:** Low risk likelihood

### Analysis details

- Allows access to all websites, posing a significant security risk as it can monitor and modify data from any visited site.
- This extension has low user count. Unpopular extensions may not be stable or safe.

> Some risk analysis details are omitted from this free response. [Upgrade to view the full analysis](https://chrome-stats.com/pricing).

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Source: [Chrome-Stats](https://chrome-stats.com/d/messpostage)