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OWASP Cheat Sheet Series · 1 min read

HTML5 Security Cheat Sheet: Web Messaging

OWASP explains origin checks, expected message formats and treating exchanged content as data. These controls address different assumptions at browser communication boundaries.

Open the reference Implementation GuideReviewed 2026-10-02

How to use this reference

Document the expected sender, operation, recipient and permitted data for browser messages. Review identity checks, data validation, application authorization and rendering safety separately in owned application designs.

Before reading

  • Basic browser origin and document concepts
  • Familiarity with event-driven JavaScript

Context and limits

  • Living guidance; review supported browser behavior and application context before implementation.
  • Origin and format validation do not by themselves define which business operations or disclosures are authorized.

Related visual models

An incoming browser message first passes origin, sender-context and format validation. A separate decision checks the operation and recipient. Failed checks reject the message without disclosure or state change. Approved content remains data and only the permitted action is performed.

Conceptual model Diagram

Browser messages need separate trust checks

Original defensive model combining OWASP messaging and authorization guidance with the linked historical cases. These are independent design checks, not a vendor patch diagram or an operational reproduction.

Reviewed 2026-10-02Read

Sources and provenance

  1. HTML5 Security Cheat Sheet: Web Messaging OWASP Cheat Sheet Series · reviewed 2026-10-02

Record reviewed 2026-10-02. Snapshot 53796974ace8. Open the complete JSON contract.

GitHub snapshot 2026-10-04

53796974ace8 · JSON exports & schemas · CC BY 4.0 content / MIT software